A Preview of Thornton's June Weather - The Severe Weather Month

June is historically Denver’s severe weather month and severe thunderstorms, tornadoes and hail are notorious visitors to Denver and across eastern Colorado during the month.  In fact, over 40 percent of the tornadoes that occur in Colorado are observed in June and these are typically the most destructive of the year.  Severe thunderstorms have also caused major property damage across the Front Range during the month.

In just the last 25 years or so, there have been some particularly notable storms in June.  Tornadoes have struck the metro area including one that longtime Thornton residents will recall on June 3, 1981.  53 residents were injured, 25 homes were destroyed and 239 other structures were damaged.  Other tornadoes in the metro area include southeast Denver and Aurora on June 8, 1986 and east Denver on June 13, 1984.  

Severe thunderstorms occurring on June 13, 1984 dumped large hail making it one of the worst and the second costliest storm in Denver history.  More recently, on June 20, 2001, a major hail storm moved across Denver International Airport dropping hailstones as big as two inches in diameter. Damage was extensive on and near the airport.

Despite the frequent tornadoes in June, due to the large areas of rural and unpopulated land there has never been a fatality in June due to a tornado.  Lightning on the other hand has caused several fatalities. 

Think we are done with the cold and snow now that June is here?  Most likely yes however cool weather can still occur early in the month.  The latest freeze on record in Denver occurred just last year on June 8, 2007 when the official low reached 31 degrees.  On June 2, 1951 the mercury dropped to 30 degrees –the record low temperature for June.  As for snow, June 11, 1947 actually saw a trace of snow fall! 

The wettest June was 1882 with 4.96 inches and the driest June was 1890 with only a trace of precipitation recorded. The maximum 24 hour precipitation was 3.16 inches on June 11, 1970 – that is a lot of rain for this area! 

Warmer temperatures are the norm though and by the end of the month temperatures can and have climbed above 100 degrees.  June 26, 1994 saw a record June temperature of 104 degrees.  Other dates with 100 degrees or higher include 102 on June 23rd 1954, June 27th 1990, June 29th 1990 and June 30th 1990 and 100 degrees set June 25th 1991.   The warmest June occurred in 1994 with an average temperature of 73.5 degrees. The coldest June was 60.6 degrees in 1967.

June 2003 was notable as it was the first June since 1972 with no 90 degree temperatures recorded. Just the year before, June 2002 had 17 90 degree days and June 2001 totaled out with 12 90 degree days.  On average June will have 6 days with above 90 degree temperatures. 

June 2006 saw us have one of the hottest June’s on record when the high temperature at the Denver International Airport reached into the nineties for 19 days.  This takes June 2006 into the record books with the most days having 90 degrees or above. The previous record for total number of 90 degree days for June was 17 occurrences established in 2002.  Also during June 2006, a record setting temperature of 102 degrees was recorded on the 14th of the month – the earliest June date that 100 degrees or higher was registered.  June 2006 was on track to become the Denver's warmest June but 3 days with highs in the 70s and several low temperature readings in the 40s and low 50s dropped the month into a tie as the 3rd warmest Denver June.

More recently, June 2009 brought an extraordinary amount of precipitation to the Denver area as 4.86 inches of rain was collected in the rain bucket. This was the second wettest June since 1872.

Looking Back at June 2010

For the most part June 2010 was pretty typical of the weather we expect to see this part of the year. 

Temperatures started out cooler than normal but by the second half of the month had warmed up.  The average temperature was 68.9 degrees which was 1.3 degrees above the historical normal but not near warm enough to make the top 10 list. 

The warmest temperature of the month was 99 degrees which occurred on the 25th while the lowest was 47 degrees which was hit on four different days.  Ten days saw temperatures over 90 degrees which was four more than normal. 

Only one temperature record was made during the month.  The high of 93 degrees on the 4th tied the record high for that date last set in 1990. 

Here in Thornton our numbers were reasonably close to those recorded at DIA.  We saw an average temperature of 68.2 degrees with a maximum of 96.0 on the 25th and a low of 46.9 degrees on the 13th.  We recorded seven days with temperatures at or above 90 degrees. 

In terms of precipitation June 2010 recorded 1.60 inches which was only 0.04 inch above normal.  Most of that fell in the period between the 11th and the 12th of the month when 1.25 inches of rainfall occurred. 

Thornton saw considerably more precipitation than what was measured at DIA as we recorded 3.10 inches.  The majority of that was measured over the four day period from the 10th to the 13th with almost half of the month's total falling on the 11th. 

Hail and a funnel cloud were recorded on the 11th by the observers at Denver International Airport.  Overall DIA observed eight thunderstorms with just the one day of hail. 

On June 10th a thunderstorm caused damage in the northeast part of Thornton as hail the size of golf balls rained down.  Vehicles took a hard hit from the hail stones as did homes and insurance companies were suddenly busy in the area assessing the damage. 

• View the ThorntonWeather.com June 2010 climate summary here

The Outlook for June 2011

National Weather Service models point to at or slightly above normal temperatures for June 2011 while precipitation models do not favor any particular trend.  As always, historical normals (below) should be used for guidance.

For More Information

Temperature Normals and Extremes for June

Monthly Temperature, Rainfall and Snowfall Extremes for June

JUNE AVERAGE STATISTICS * Normals & Means, 1971 - 2000
TEMPERATURE
AVERAGE HIGH	82.1
AVERAGE LOW	53.0
MONTHLY MEAN	67.6
DAYS WITH HIGH 90 OR ABOVE	6
DAYS WITH HIGH 32 OR BELOW	0
DAYS WITH LOW 32 OR BELOW	0
DAYS WITH LOWS ZERO OR BELOW	0
PRECIPITATION
MONTHLY MEAN	1.56 INCHES
DAYS WITH MEASURABLE PRECIPITATION	9
AVERAGE SNOWFALL	TRACE (Includes hail reports)
DAYS WITH 1.0 INCH OR MORE SNOWFALL	0
MISCELLANEOUS JUNE AVERAGES
HEATING DEGREE DAYS	60
COOLING DEGREES DAYS	136
WIND SPEED (MPH)	8.9 MPH
WIND DIRECTION	SOUTH
DAYS WITH THUNDERSTORMS	10
DAYS WITH DENSE FOG	0* (Less than 1)
PERCENT OF SUNSHINE POSSIBLE	70
JUNE EXTREMES
RECORD HIGH	104 ON 6/26/1994
RECORD LOW	30 ON 6/2/1951
WARMEST	73.5 IN 1994
COLDEST	60.6 IN 1967
WETTEST	4.96 INCHES IN 1882
MAXIMUM 24 HOUR MOISTURE	3.16 INCHES IN 1970
DRIEST	TRACE IN 1890
SNOWIEST (Could include hail)	0.4 INCH IN 1919 0.3 INCH IN 1951 TRACE IN 1974, 1947, 1937, 1917
LEAST SNOWIEST	0.0 INCH EXCEPT FOR THOSE YEARS LISTED ABOVE

* Historical weather statistics gathered from the National Weather Service's Denver / Boulder forecast office data archives.