June 2009 went down in the history books as one of the more unusual June’s on record.  Residents are all of course well aware of the string of severe storms but the Mile High City also were unusually cool and certainly very wet. 

In terms of precipitation, a whopping 4.86 inches of rain fell at the official measuring site at Denver International Airport during the month – the second wettest June since recordkeeping began here in 1872.  We missed out on breaking the record by only a tenth of an inch as the all-time wettest was back in 1882 when 4.96 inches fell in the rain bucket.  Nevertheless, we easily exceed the normal rainfall total for the month which is 1.56 inches.  In fact, we beat that in one day on June 23rd when 1.64 inches fell at DIA.  Here in Thornton we didn’t measure near as much precipitation having recording 3.44 inches for the month.  This is more in line with what areas closer to the actual metro area recorded than what was recorded at DIA.  See below for details on the controversy about Denver’s climate records. 

Temperature wise, we were very cool as well, never breaking the 90 degree mark during the month.  Two days, the 29th and 30th, came close with 89 degrees being recorded as the high temperatures on those days.  This was the first time since 2003 no 90 degree days were recorded in June.  Before that, you would have to go way back to 1972 to find another June when that happened.  The average temperature for June 2009 was 64.4 degrees, 3.2 degrees below the normal of 67.6.  That may be cool but it was nowhere near the record low average for June which is 60.6 set in 1967.  Thornton was just a touch warmer than the official stats from DIA as we recorded 90.0 degrees on the 29th.  Similarly, Thornton’s average temperature was just a bit cooler at 63.2 degrees. 

Then of course there were the storms.  Tornadoes, funnel clouds and hail will probably be the most memorable events of the month, especially the twister that struck the Southlands Shopping Center in Aurora.  In all, DIA recorded 18 days with thunderstorms – eight more than normal.  15 days had precipitation versus the normal of nine.  All those storms also took a toll on what is normally a sunny month.  On average Denver has 70 percent of possible sunshine during the month.  This year we only recorded sunshine 51 percent of the time. 

All that rain we have received in the last two months, especially in June, helps to make one other statistic a bit more tolerable.  Colorado’s snow season runs from July 1 to June 30 each year and for the 2008 – 2009 snow season, we recorded a meager 38.1 inches of the white stuff.  That is a whopping 29 inches below the normal of 67.1 inches.   Thornton fared a bit better on the snowfall front but not by a lot having recorded 48.5 inches for the season.

There is always a ‘but’… 

As always, we would like to remind everyone that all official Denver weather statistics are now taken out at Denver International Airport.  As we outlined a few months ago, moving the official monitoring station 13 miles away has made quite a difference in Denver’s climate records.  Evidence suggests that temperatures and precipitation as measured at DIA differ greatly from what would have been recorded at the old site at Stapleton or near downtown Denver. 

• For more on the controversy about Denver’s climate records, visit our story on Examiner.com – Do Denver weather records have an asterisk attached?

The National Weather Service has finally acknowledged this and has setup a measuring station at the Denver Museum of Nature and Science (click here to view current conditions from it on the Weather Underground).  However, they maintain that Denver’s official statistics will continue to be recorded at DIA and as a result, Denver’s climate records will forever have an asterisk next to them.  If you compare June’s statistics from this new station to the ‘official’ ones at DIA, you will notice that much of what we discuss above, including the temperature and precipitation, would be much different were the statistics being kept by the new station closer to where people actually live.

Denver climate summary for the month of June 2009 – From the National Weather Service

CLIMATE NORMAL PERIOD 1971 TO 2000
CLIMATE RECORD PERIOD 1872 TO 2009
WEATHER         OBSERVED          NORMAL  DEPART  LAST YEAR'S
                 VALUE   DATE(S)  VALUE   FROM    VALUE  DATE(S)
                                          NORMAL
................................................................
TEMPERATURE (F)
RECORD
 HIGH             104   06/26/1994
 LOW               30   06/02/1951
HIGHEST            89   06/30       104     -15       95  06/26
                        06/29
LOWEST             41   06/08        30      11       37  06/12
AVG. MAXIMUM     77.7              82.1    -4.4     83.9
AVG. MINIMUM     51.1              53.0    -1.9     50.9
MEAN             64.4              67.6    -3.2     67.4
DAYS MAX >= 90      0               6.3    -6.3       10
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         4.96   1882
 MINIMUM            T   1890
TOTALS           4.86              1.56    3.30     0.73
DAILY AVG.       0.16              0.05    0.11     0.02
DAYS >= .01        15               8.7     6.3        4
DAYS >= .10         9                MM      MM        2
DAYS >= .50         4                MM      MM        1
DAYS >= 1.00        1                MM      MM        0
GREATEST
 24 HR. TOTAL    1.64R  06/23 TO 06/23              0.70     06/04 TO 06/05       

SNOWFALL (INCHES)
RECORDS
 TOTAL            0.4   1919
TOTALS            0.0                T
DEGREE_DAYS
HEATING TOTAL      78                60      18       64
 SINCE 7/1       5616              6128    -512     6056
COOLING TOTAL      68               136     -68      144
 SINCE 1/1         94               161     -67      172
FREEZE DATES
RECORD
 EARLIEST     09/08/1962
 LATEST       06/02/1951
EARLIEST                        10/07
LATEST                          05/05
.................................................................
WIND (MPH)
AVERAGE WIND SPEED              8.4
RESULTANT WIND SPEED/DIRECTION   2/147
HIGHEST WIND SPEED/DIRECTION    53/260    DATE  06/26
HIGHEST GUST SPEED/DIRECTION    68/270    DATE  06/26
SKY COVER
POSSIBLE SUNSHINE (PERCENT)   51
NUMBER OF DAYS FAIR            3
NUMBER OF DAYS PC             22
NUMBER OF DAYS CLOUDY          5
AVERAGE RH (PERCENT)     65
WEATHER CONDITIONS. NUMBER OF DAYS WITH
THUNDERSTORM             18     MIXED PRECIP               1
HEAVY RAIN                7     RAIN                      10
LIGHT RAIN               17     FREEZING RAIN              0
LT FREEZING RAIN          0     HAIL                       3
HEAVY SNOW                0     SNOW                       0
LIGHT SNOW                0     SLEET                      0
FOG                      14     FOG W/VIS <= 1/4 MILE      6
HAZE                     10                                           

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