June 2021 began as one of the hottest and driest on record for the area, but ended on a cool and rainy note! Other weather highlights during the month included a slew of new wildfires across the Western Slope, a highly photogenic landspout tornado, multiple heatwaves, and poor air quality from near and distant wildfires. Here’s a quick and colorful recap of our weather during June and how it relates to climatology.

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Top Weather Highlights of June 2021:

WET SPRING = DEEP SNOWPACK:  A wet spring across the Front Range, especially in April and May, led to deep late season snowpack in some areas. While the rest of the state had fairly dismal snowpack in early June, the South Platte River Basin was well above normal.

TRANSPLANT SMOKE: With several large wildfires burning out of state mainly in Arizona, when the large-scale pattern shifted to southwest flow across Colorado this month all that smoke invaded the Front Range. Most of the smoke during the early to middle part of the month was elevated and only caused minor drops in visibility.

THE MOST VIEWED TORNADO EVER? On June 7th, severe weather was not expected at all across the Front Range, but Mother Nature had other ideas spawning a landspout tornado. Colliding outflow boundaries from weak thunderstorms aligned just right to create a tornado east of Longmont in Weld County which moved northward. This tornado was rated EF1 by the National Weather Service and was on the ground for at least 7 miles causing minor structural damage and killing some livestock.

Not only was this tornado unique for the conditions that created it, it was also extremely photogenic! It was potentially visible to nearly 50% of the population of the Denver Metro area due to the isolated nature of the storms that day and the extremely high cloud base of the tornadic thunderstorm.

A LONG-DURATION HEATWAVE: Two separate heatwave patterns blended together to produce a 15-day long period of above normal temperatures across eastern Colorado (June 4th to June 19th).

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While hot, this particular heatwave was stronger in the Desert Southwest than it was in Colorado. Because of this, we predicted that Boulder would not reach the relatively rare 100-degree mark during this stretch. Boulder peaked at 99°F on two separate days (June 16th & 17th), while Denver made it to the triple digits on three consecutive days (June 15th – 17th).

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In case you are wondering, 100-degree days are relatively rare in Boulder, happening only 45 times in the last 125 years (about once every 3 years).

With the prolonged hot weather to start the month, June 2021 was actually on pace for a Top 10 finish for hottest Junes through the 20th in Boulder.

COLORADO NATIVE SMOKE: Towards the end of the heatwave (which one?), several wildfires ignited across western Colorado and began contributing just as much smoke, if not more, than the larger out-of-state fires. The result was an extended period of thicker and lower-level smoke across the Denver Metro area.

Several days in a row had poor air quality due to secondary ozone concentration spikes from the smoke.

Visible satellite image from June 21, 2021 orf at least 6 wildfires burning in western Colorado

MAJOR COOLDOWN TO END THE MONTH: June wrapped up with a big pattern shift that brought cooler temperatures to most of Colorado while an historic, deadly heatwave raged across the Pacific Northwest and parts of southwestern Canada. Boulder concluded the month with seven straight days of below normal temperatures. This weeklong cool and rainy stretch knocked June 2021 out of contention for the hottest and driest Junes on record in Boulder. With half of 2021 complete, Boulder has a nearly 4″ surplus in precipitation for the year.

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June 2021 Recap Graphics:

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Thanks to Larry Pierce for the featured image of smoke and moon. 

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This post had major contributions from at least two members of our team. The more meteorologists the better, right?

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