Category Archives: Climatology

Climatology, Thornton Weather

No October snow in Denver? Not unusual at all

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The lack of measurable snow this October is not all that unusual. Click for larger view.
The lack of measurable snow this October is not all that unusual. Click for larger view.

October will end with Denver not having seen any snow accumulation at all during the month.  While that, coupled with the overall lack of precipitation is concerning, not having snow is not at all unusual.

On average, the Mile High City receives 4.2 inches during October.

However, since record-keeping began in 1882, the month failed to yield any snow at all in 19 years since.  Further, in another 17 of those years we only received a trace.

This means that in 27% of the past 134 years, we saw essentially no accumulating snow in October.  So, the fact we won’t have received any this month is not uncommon.

The average date for our first snowfall is October 18th so we aren’t running all that far behind.  The earliest seasonal snowfall came on September 3, 1961 and the latest on November 21, 1934.

We have been exceedingly dry, really since the first part of June.

In October, Denver has recorded a mere 0.26 inches of precipitation while here in Thornton we have fared better with 0.43 inches.  On average we expect to see 0.97 inches so both locations are well below normal.

Perhaps more notable than the lack of moisture is the temperatures which have been unseasonably warm.

As of right now, the average temperature for the month is at 57.2 degrees in Denver, 55.1 degrees in Thornton.  This is running far above the historical October average temperature of 50.9 degrees.

Depending on temperatures between now and the end of the month, it is looking likely that October 2016 will finish somewhere in the top five or six warmest Octobers on record.

Climatology, National Weather, Thornton Weather

NOAA releases 2016 – 2017 winter weather outlook

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What will this winter have in store for Thornton?  Forecasters at the Climate Prediction Center have released their outlook and for the Front Range, it doesn’t hold much in the way of clues.

The CPC does show odds favor above average temperatures for much of Colorado for the period from December through February.  In terms of precipitation, the agency gives equal chances of near average, well above average, or well below average precipitation for most of the state. The one exception is the southern third of Colorado which they peg at having above average chances of a drier than normal year.

From NOAA:

U.S. Winter Outlook predicts warmer, drier South and cooler, wetter North
Drought expected to persist in California and expand in the Southeast

Winter 2016 - 2017 temperature outlook. Click for larger view. (NOAA)
Winter 2016 – 2017 temperature outlook. Click for larger view. (NOAA)

October 20, 2016 – Forecasters at NOAA’s Climate Prediction Center issued the U.S. Winter Outlook today, saying that La Nina is expected to influence winter conditions this year. The Climate Prediction Center issued a La Nina watch this month, predicting the climate phenomenon is likely to develop in late fall or early winter. La Nina favors drier, warmer winters in the southern U.S and wetter, cooler conditions in the northern U.S. If La Nina conditions materialize, forecasters say it should be weak and potentially short-lived.

“This climate outlook provides the most likely outcome for the upcoming winter season, but it also provides the public with a good reminder that winter is just up ahead and it’s a good time to prepare for typical winter hazards, such as extreme cold and snowstorms,” said Mike Halpert, deputy director, NOAA’s Climate Prediction Center. “Regardless of the outlook, there is always some chance for extreme winter weather, so prepare now for what might come later this winter.”

Other factors that often play a role in the winter weather include theArctic Oscillation, which influences the number of arctic air masses that penetrate into the South and create nor’easters on the East Coast, and the Madden-Julian Oscillation, which can affect the number of heavy rain events in the Pacific Northwest.

The 2016 U.S. Winter Outlook (December through February):

Winter 2016 - 2017 precipitation outlook. Click for larger view. (NOAA)
Winter 2016 – 2017 precipitation outlook. Click for larger view. (NOAA)

Precipitation

  • Wetter than normal conditions are most likely in the northern Rockies, around the Great Lakes, in Hawaii and in western Alaska
  • Drier than normal conditions are most likely across the entire southern U.S. and southern Alaska.

Temperature

  • Warmer than normal conditions are most likely across the southern U.S., extending northward through the central Rockies, in Hawaii, in western and northern Alaska and in northern New England.
  • Cooler conditions are most likely across the northern tier from Montana to western Michigan.
  • The rest of the country falls into the “equal chance” category, meaning that there is not a strong enough climate signal in these areas to shift the odds, so they have an equal chance for above-, near-, or below-normal temperatures and/or precipitation.

Drought

  • Drought will likely persist through the winter in many regions currently experiencing drought, including much of California and the Southwest
  • Drought is expected to persist and spread in the southeastern U.S. and develop in the southern Plains.
  • New England will see a mixed bag, with improvement in the western parts and persistence to the east.  
  • Drought improvement is anticipated in northern California, the northern Rockies, the northern Plains and parts of the Ohio Valley.

This seasonal outlook does not project where and when snowstorms may hit or provide total seasonal snowfall accumulations. Snow forecasts are dependent upon the strength and track of winter storms, which are generally not predictable more than a week in advance.  However, La Nina winters tend to favor above average snowfall around the Great Lakes and in the northern Rockies and below average snowfall in the mid-Atlantic.

NOAA produces seasonal outlooks to help communities prepare for what’s likely to come in the next few months and minimize weather’s impacts on lives and livelihoods. Empowering people with actionable forecasts and winter weather tips is key to NOAA’s effort to build aWeather-Ready Nation.

Climatology, Thornton Weather

Thornton’s October 2016 preview: Fall returns, hopefully with precipitation

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Thornton, Colorado October weather preview.With the first full month of fall here, October usually brings one of the quietest weather months in the Denver area with plenty of mild, sunny days and clear, cool nights. Given the lack of precipitation of the last few months though, we certainly would welcome some moisture.

October is historically the second sunniest month and conditions are generally calm.

However we also will usually see our first taste of winter during the month with the first freeze and first snowfall of the season.  Temperatures as well will start to drop and by the end of the month the average nighttime lows are below freezing.

For complete details on our historical October weather and what we can expect in the coming month, read our complete October weather preview here.

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Climatology, Thornton Weather

September 2016 weather recap: A very dry month with near normal temperatures

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The month of September was overall a pleasant one however that came at a price.  A very distinct lack of precipitation led to dry conditions, a trend that had started earlier in the summer.

High pressure was the general rule for the month and that helped to ensure that any significant weather potential was steered away from the state.  A few troughs and cold fronts mixed things up but in the end, we only saw precipitation on three days during the month and the amounts were negligible.

Thornton’s average temperature for the month came in at 63.7 degrees.  This was just slightly above Denver’s long term average for September of 63.4 degrees.  Out at the airport where Denver’s official measurements are taken, it was a good bit warmer with an average of 66.0 degrees.

Temperatures here ranged from a high of 91.6 degrees on the 5th of the month down to a low of 39.8 degrees on the 24th.  DIA recorded a maximum of 93 degrees, also on the 5th, and a low of 37 degrees on the 10th.

In terms of precipitation, Thornton saw a measly 0.05 inches fall into our rain bucket.  The airport fared far better with 0.28 inches.  However, both measurements were well below the September average for Denver of 0.96 inches.  The reading in Thornton would have been low enough to tie for the third driest reading in Mile High City history.

Click here to view Thornton’s September 2016 climate report.

Thornton, Colorado's September 2016 temperature summary. (ThorntonWeather.com)
Thornton, Colorado’s September 2016 temperature summary. (ThorntonWeather.com)
Thornton, Colorado's September 2016 precipitation summary. (ThorntonWeather.com)
Thornton, Colorado’s September 2016 precipitation summary. (ThorntonWeather.com)

From the National Weather Service:

CLIMATE REPORT
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
933 AM MDT SAT OCT 1 2016

................................... 

...THE DENVER CO CLIMATE SUMMARY FOR THE MONTH OF SEPTEMBER 2016... 

CLIMATE NORMAL PERIOD 1981 TO 2010
CLIMATE RECORD PERIOD 1872 TO 2016

WEATHER         OBSERVED          NORMAL  DEPART  LAST YEAR`S
                 VALUE   DATE(S)  VALUE   FROM    VALUE  DATE(S)
                                          NORMAL
................................................................ 
TEMPERATURE (F)
RECORD
 HIGH              97   09/06/2013
                        09/05/2013
                        09/04/1995
 LOW               17   09/29/1985
HIGHEST            93   09/05        91       2       92  09/02
LOWEST             37   09/10        35       2       44  09/19
AVG. MAXIMUM     82.3              78.5     3.8     85.2
AVG. MINIMUM     49.7              48.3     1.4     53.5
MEAN             66.0              63.4     2.6     69.4
DAYS MAX >= 90      6               3.4     2.6        7
DAYS MAX <= 32      0               0.0     0.0        0
DAYS MIN <= 32      0               0.8    -0.8        0
DAYS MIN <= 0 0 0.0 0.0 0 PRECIPITATION (INCHES) RECORD MAXIMUM 5.61 2013 MINIMUM T 1892 1944 TOTALS 0.28 0.96 -0.68 0.11 DAILY AVG. 0.01 0.03 -0.02 0.00 DAYS >= .01         4               6.5    -2.5        3
DAYS >= .10         1               3.3    -2.3        0
DAYS >= .50         0               0.6    -0.6        0
DAYS >= 1.00        0               0.1    -0.1        0
GREATEST
 24 HR. TOTAL    0.18   09/12 TO 09/12           08/31 TO 09/01

SNOWFALL (INCHES)
RECORDS
 TOTAL            0.0              1.3
RECORD SEPTEMBER 17.2                      1971

DEGREE_DAYS
HEATING TOTAL      64               125     -61        9
 SINCE 7/1         79               141     -62       27
COOLING TOTAL      99                76      23      148
 SINCE 1/1        861               764      97      861

FREEZE DATES
RECORD
 EARLIEST     09/08/1962
 LATEST       06/08/2007
EARLIEST                        10/07
LATEST                          05/05
..................................................... 

WIND (MPH)
AVERAGE WIND SPEED              9.5
RESULTANT WIND SPEED/DIRECTION   2/171
HIGHEST WIND SPEED/DIRECTION    37/170    DATE  09/23
HIGHEST GUST SPEED/DIRECTION    51/200    DATE  09/04

SKY COVER
POSSIBLE SUNSHINE (PERCENT)   MM
AVERAGE SKY COVER           0.40
NUMBER OF DAYS FAIR           13
NUMBER OF DAYS PC             13
NUMBER OF DAYS CLOUDY          4

AVERAGE RH (PERCENT)     45

WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM              6     MIXED PRECIP               0
HEAVY RAIN                0     RAIN                       0
LIGHT RAIN                6     FREEZING RAIN              0
LT FREEZING RAIN          0     HAIL                       0
HEAVY SNOW                0     SNOW                       0
LIGHT SNOW                0     SLEET                      0
FOG                       4     FOG W/VIS <= 1/4 MILE      3
HAZE                      4

-  INDICATES NEGATIVE NUMBERS.
R  INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T  INDICATES TRACE AMOUNT.
Climatology, Thornton Weather

September preview: The end of summer brings one of our most pleasant months

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Following on what was a cool but dry August, some are certainly hoping for a bit of precipitation.  The month can bring plenty of rain and even our first snow of the season but more often than not, it is one of the most pleasant along the Colorado Front Range.

As temperatures start to drop, September usually reminds us that summer is at an end and fall is now here. Sunshine is predominant though as the month actually has the highest percentage of sun out of any month. Sunny days and clear, cool nights are the standard weather pattern for the month.

The month can bring extremes however.  We will of course forever remember last year’s devastating floods brought on by record-setting rain.  Longtime residents might remember September 1971 which brought over 17 inches of snowfall.

Get a complete look at September’s weather and more details as to what we can expect this year here.

Climatology, Thornton Weather

July 2016 weather recap: Thornton sees near normal temps, below average precipitation

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While the month of July seemed hot and dry, statistics show that only one of those two conditions held true.  We definitely saw a big time lack of precipitation but temperatures averaged out to near normal.

High pressure was the dominate feature for the month leading to overall dry conditions.  We started out cooler than normal and somewhat wet for the first two days of the month. That however changed quickly.

From the 3rd through the 17th of the month, Thornton saw temperatures largely remain above normal.  Only two days during that period saw precipitation and both were minimal amounts.  We saw our hottest temperature of the year to date and our only 100-degree temperature reading of the year on the 10th when the mercury topped out at 100.4 Degrees.

On the 14th and 15th of the month, we had a brief respite from the heat as temperatures were a bit below normal.  However, we then put together a string of 12 straight days of 90 degree or hotter readings.

The 28th and 29th then broke the streak with temperatures in the mid to upper 80s.  The month then closed with two days of above normal readings.

Thornton’s overall average temperature for the month came in at 74.7 degrees.  This is just above the long term Denver average for July of 74.2 degrees.  Out at DIA where the Mile High City’s official measurements are taken, the average for this July was much higher at 76.2 degrees.

Temperatures in Thornton ranged from the aforementioned 100.4 degrees on the 10th down to a low of 54.6 degrees on the morning of the 9th.  Denver’s official high for the month was 102 degrees on the 10th and its low of 51 degrees came on the 12th.

In terms of precipitation, Denver averages 2.16 inches during the July.  Thornton fell far short of that with a paltry 0.55 inches of rain in our bucket.  The airport, while receiving nearly double our total at 1.09 inches, was well short of average as well.

Click here to view Thornton’s July 2016 climate report.

Thornton, Colorado's July 2016 temperature summary. (ThorntonWeather.com)
Thornton, Colorado’s July 2016 temperature summary. (ThorntonWeather.com)
Thornton, Colorado's July 2016 precipitation summary. (ThorntonWeather.com)
Thornton, Colorado’s July 2016 precipitation summary. (ThorntonWeather.com)

From the National Weather Service:

CLIMATE REPORT
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
235 AM MDT MON AUG 1 2016

................................... 

...THE DENVER CO CLIMATE SUMMARY FOR THE MONTH OF JULY 2016... 

CLIMATE NORMAL PERIOD 1981 TO 2010
CLIMATE RECORD PERIOD 1872 TO 2016

WEATHER         OBSERVED          NORMAL  DEPART  LAST YEAR`S
                 VALUE   DATE(S)  VALUE   FROM    VALUE  DATE(S)
                                          NORMAL
................................................................ 
TEMPERATURE (F)
RECORD
 HIGH             105   07/20/2005
 LOW               42   07/04/1903
                        07/31/1873
HIGHEST           102   07/10         M      -3       97  07/27
LOWEST             51   07/12         M       9       52  07/28
AVG. MAXIMUM     92.0              89.4     2.6     87.6
AVG. MINIMUM     60.5              58.9     1.6     57.9
MEAN             76.2              74.2     2.0     72.8
DAYS MAX >= 90     22              16.0     6.0       16
DAYS MAX <= 32      0               0.0     0.0        0
DAYS MIN <= 32      0               0.0     0.0        0
DAYS MIN <= 0       0               0.0     0.0        0

PRECIPITATION (INCHES)
RECORD
 MAXIMUM         6.41   1965
 MINIMUM         0.01   1901
TOTALS           1.07              2.16   -1.09     1.06
DAILY AVG.       0.03              0.07   -0.04     0.03
DAYS >= .01         6               8.3    -2.3       12
DAYS >= .10         4               4.3    -0.3        3
DAYS >= .50         1               1.4    -0.4        0
DAYS >= 1.00        0               0.7    -0.7        0
GREATEST
 24 HR. TOTAL    0.61   07/01 TO 07/01           07/18 TO 07/18
                        06/30 TO 07/01                    07/29 TO 07/29
                        07/01 TO 07/01                    07/29 TO 07/29
 STORM TOTAL       MM                                 MM
 (MM/DD(HH))            MM                    07/18(00) TO 07/18(00)
                                                 07/29(00) TO 07/29(00)9
                                                 07/29(00) TO 07/29(00)9

SNOWFALL (INCHES)
RECORDS
 TOTAL             MM   MM
TOTALS            0.0               0.0

DEGREE_DAYS
HEATING TOTAL       0                 6      -6        5
 SINCE 7/1          0                 6      -6        5
COOLING TOTAL     356               289      67      251
 SINCE 1/1        544               444     100      409

FREEZE DATES
RECORD
 EARLIEST     09/08/1962
 LATEST       06/08/2007
EARLIEST                        10/07
LATEST                          05/05
.......................................................... 

WIND (MPH)
AVERAGE WIND SPEED              10.2
RESULTANT WIND SPEED/DIRECTION   3/169
HIGHEST WIND SPEED/DIRECTION    54/340    DATE  07/24
HIGHEST GUST SPEED/DIRECTION    74/340    DATE  07/24

SKY COVER
POSSIBLE SUNSHINE (PERCENT)   MM
AVERAGE SKY COVER           0.50
NUMBER OF DAYS FAIR           10
NUMBER OF DAYS PC             19
NUMBER OF DAYS CLOUDY          2

AVERAGE RH (PERCENT)     46

WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM             12     MIXED PRECIP               0
HEAVY RAIN                1     RAIN                       0
LIGHT RAIN               13     FREEZING RAIN              0
LT FREEZING RAIN          0     HAIL                       0
HEAVY SNOW                0     SNOW                       0
LIGHT SNOW                0     SLEET                      0
FOG                       3     FOG W/VIS <= 1/4 MILE      0
HAZE                      1

-  INDICATES NEGATIVE NUMBERS.
R  INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T  INDICATES TRACE AMOUNT.
Climatology, Thornton Weather

Thornton’s August preview: Temperatures cool, severe weather eases

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As summer vacations wind down and families prepare to send their kids back to school in August, Colorado weather also starts to settle down. The chances for severe weather decrease markedly during August and by the end of the month daytime temperatures are dropping quite a bit as well.

Find out more about what lies ahead with Thornton’s August weather here.

Climatology, Thornton Weather

July weather preview: Hot temperatures, PM thunderstorms

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Change is of course the one constant in Denver’s weather but come July, things actually get pretty consistent.

The standard formula for a day in July is a sunny morning, clouds developing in the late morning and early afternoon. Come mid-afternoon, thunderstorms are rolling off of the foothills and into the metro area and the eastern plains. These storms do occasionally reach severe status containing hail, gusty winds and heavy downpours of rain.

Check out our July weather preview for a complete look at what is in store for the month ahead.

Climatology, Thornton Weather

Thornton’s 2015 – 2016 seasonal snowfall totals end far above average

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Thornton, Colorado monthly and seasonal snowfall totals from the 2006 / 2007 season to the the 2015 / 2016 season. (ThorntonWeather.com)
Thornton, Colorado monthly and seasonal snowfall totals from the 2006 / 2007 season to the the 2015 / 2016 season. Click for larger view. (ThorntonWeather.com)

To say we had a lot of snow this past season would be a bit of an understatement.  Our total came in at more than 2 feet higher than historical average for Thornton and Denver.

In all, Thornton received 85.7 inches of snowfall for the 2015 / 2016 season.  That total eclipses the 10-year Thornton average of 58.0 inches and Denver’s official 30-year average (1981 – 2010) of 55.3 inches.

The measurement is also Thornton’s highest snowfall total of the past 10 years since ThorntonWeather.com came into existence.  The next highest seasonal total is the 72.9 inches received during the 2006 / 2007 season.

Thornton saw five months with above normal snowfall.  Most notable was November which received nearly 10 inches more than normal and March with 18.9 inches more than average.

Denver’s official seasonal total was well above normal as well.  Out at Denver International Airport where the measurements are taken, The National Weather Service reported 72.8 inches.

It is likely if the Mile High City’s measurements were still done at a location in the city, the total would have been a good bit higher.

Climatology

Thornton’s June weather preview: Severe weather becomes the talk of the town

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Thornton's June weather preview.Extreme weather can occur during in month in Colorado we well know.  June however is when traditional spring severe weather arrives in the state oftentimes with hail, damaging wind and tornadoes.

Over 40 percent of the tornadoes that occur in Colorado happen during the month of June.  Far more common are thunderstorms with hail and wind, each responsible for extensive damage each year.

While severe weather is common, so too are brilliantly sunny and mild days as we close out spring and enter summer.  If you are looking for cold, it isn’t likely but it is possible as the Denver area has seen freezing temperatures and yes, even snow, during the month.

Read more about Thornton and Denver’s June weather and a look ahead at this year.