Welcome to June in Denver! A month that acts like summer most of the time but isn’t afraid to show its brooding spring-like contempt whenever it feels the need—and it usually delivers those punches in the form of thunderstorms and large hail.
Like most of spring, June is a transitional month. It’s a month that lies between the cool rains of May and the warm rains of the monsoon season. Warm Gulf moisture will occasionally pick fights with cold fronts, creating periods of instability, thunderstorms, hail, and sometimes tornadoes.
Denver7 Chief Meteorologist Mike Nelson provides an outlook on June weather and explains some of the extreme weather statistics for the month. Watch the video in the player below:
The month can receive the most intense severe weather of the year, according to the National Weather Service. Tornado season heats up as well during June. But let’s get the stats out of the way.
June is the city’s third-warmest month of the year, behind July and August. Denver`s monthly mean temperature for June is 67.4 degrees, based on averages from 1981 to 2010. We start the month with an average high of 77 degrees and end the month 10 degrees warmer on average. The hottest it’s ever gotten in June was 105 degrees for two days in a row in 2012!
Temperatures can dip down to below freezing, but it’s very rare. The coldest temperature recorded in June in Denver was 30 degrees on June 2, 1951. But we average about 48 degrees at the beginning and 56 degrees toward the end of the month as far as low temperatures are concerned.
Coming out of what is considered the wettest month of the year, May, the sixth month of the year precedes what is considered the second wettest month of the year in Denver, July. We tend to see a lot of moisture in the form of severe thunderstorms during June, after all, severe weather season is in full force.
The monthly mean for precipitation is 1.98 inches. The wettest June we saw in Denver was in 1882, when 4.96 inches of moisture fell in the city. And more recently, in 2009, we got 4.69 inches of moisture. But our driest June occurred in 1916 when only 0.08 inches of rain fell in Denver for the entire month.
And remember snow? It can happen, but it too is a very rare event. Snow has occurred only seven times in June in Denver since 1882 with the last occurrence in 1974 with a trace, according to the NWS. The Mile High City’s snowiest June happened in 1953 when a whopping total of 0.5 inches fell during the entire month.
Severe weather season
As mentioned above, June can be the most relentless month weather-wise for Denver. Severe thunderstorms with large hail, damaging wind gusts, heavy rain, and strong tornadoes are common during the sixth month of the year.
Colorado is entering peak tornado season. The state sees an average of 27 tornadoes during May and June, with June being the busiest month with an average of 17 tornadoes, according to the National Oceanic and Atmospheric Administration. There have been 2,125 tornado events recorded in Colorado and at least five deaths related to twisters since 1950.
The most tornado-prone county in Colorado — and the entire country — is Weld County, which has seen 268 tornadoes since 1950. The city and county of Denver has seen 16 tornadoes in the same period.
The biggest tornado event that struck Denver was on June 15, 1988. Seven people were injured when an F-3 tornado touched down in the southern part of the city, cutting an erratic path 2.5 miles long. The storm damaged 85 buildings and several cars and uprooted trees.
The injuries were minor, but according to NWS reports, very traumatic for some of those involved. A golfer was thrown 40 feet but was not hurt. A man clinging to a telephone pole was unscathed but lost both of his shoes. A woman holding a baby was sucked through a broken window of a convenience store, but neither the woman nor the baby was hurt.
Tornadic activity doesn't always occur in the usual places in Colorado. Although extremely rare, tornadoes and funnel clouds have been spotted on the Western Slope and in high-altitude areas. There have been three tornado touchdowns in Park County, occurring on June 8, 2014, Aug. 18, 2009, and Aug. 23, 2008. In 2011, a tornado was documented on Mount Evans with an elevation of 11,900 feet. And on June 20, 1975, an F2 tornado touched down in Pitkin County.
Damaging hail is also a concern in June. Storms can produce hailstones up to the diameter of a fully-grown grapefruit. In a typical season, which is from mid-April to mid-August, the Front Range sees about three or four catastrophic hailstorms, according to the Rocky Mountain Insurance Information Association.
Colorado, along with Nebraska and Wyoming, makes up what meteorologists call “hail alley.” The area averages seven to nine hail days per year. According to the National Severe Storms Laboratory, the reason why this area gets so much hail is that the freezing levels (the area of the atmosphere at 32 degrees or less) in the high plains are much closer to the ground than they are at sea level, where hail has plenty of time to melt before reaching the ground.
Hail is usually pea-sized to marble-sized, but big thunderstorms can produce big hail. Baseball-sized hail pounded parts of Golden and Lakewood during a record-breaking storm in 2017.
According to the Rocky Mountain Insurance Information Association, Colorado had the second-highest number of hail claims in the US from 2013 to 2015 (182,591), second only to Texas. The costliest hail storm to hit Colorado was on May 8, 2017. The Denver metro area sustained $2.3 billion in insured damage.
Prepare for severe weather
Be prepared for severe weather when it strikes. Follow these tips provided by the Colorado Office of Emergency Management:
- Build an emergency kit and make a family communications plan.
- Identify a safe shelter location – a basement is best, followed by interior rooms on the lowest level of the building away from windows. Mobile homes are often unsafe in a tornado – identify a neighbor's house or public shelter where you can go if a tornado warning is issued.
- Secure outdoor objects that could blow away or cause damage during a storm.
- Unplug any electronic equipment before the storm arrives.
- Obtain a NOAA Weather Radio (link is external) to receive alerts about impending severe weather.
- Sign up for reverse telephone alerts (link is external) for your county, and don't forget to include your cell phone.
- Make sure you have sufficient insurance coverage – including flood insurance, which is separate from your homeowners or renters policy.
- Photograph or take video footage of the contents in your home in case you need to file a claim after a disaster.
- Store copies of your important documents in another location, such as a bank safe deposit box.