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Why heat advisories are so rare in Colorado

A tweak to heat advisory criteria could increase the amount of advisories issued in Colorado.

GRAND JUNCTION, Colo. — It hit 100 degrees for the first time on the Western Slope near Grand Junction on Friday, tying the daily record last set in 1981. And there could be two more 100 degree readings over the weekend there. 

The National Weather Service issued a heat advisory that lasts through Sunday night at 9 p.m., and it includes the Grand Valley.

It’s only the eighth heat advisory on record in the state of Colorado.

Heat advisories are very unusual in our state, not because it doesn’t get hot enough during the day, but because of how fast the temperatures cool after the sun goes down. Even on our hottest days, it usually still drops below 70 degrees by morning.

That makes it difficult to hit the traditional criteria for a heat advisory, which has a minimum temperature of 75 degrees.

But that doesn’t mean heat in Colorado isn’t hazardous, so the National Weather Service in Grand Junction believes it’s time to bend the rules.

“Within the last few years, we’ve really taken a look at the thresholds and tried to tailor it to this climate and how more arid areas are affected by heat,” said meteorologist Erin Walter. "To have blanket product for areas that have so many different climatologies is a little misleading."

Walter said they are using a new guide for warning the public about extreme heat. 

The new HeatRisk product factors in things like how much warmer the temperatures are than the average, how long the heat event will last, and how much area and population the heat covers.

She said meteorologists in the Utah and Colorado offices will now be using this product to make judgment calls on when to issue heat advisories and excessive heat warnings in Colorado.

“It’s a continuous discussion with your team members that are on shift. It’s not just one person’s decision, it’s a team effort.”

There are no heat advisories on the Front Range for this weekend at this moment, but it will be possible to hit 100 degrees here on Saturday afternoon.

History of Advisories in Colorado

This new take on heat advisory criteria may lead to an increase in the amount of advisories issued, along with the trend of rising summer temperatures in the daytime and nighttime hours. 

Last year there were two heat advisories issued in Colorado. Both were on the Western Slope July 7-10.

In 2020, one heat advisory was issued for the Grand Valley Aug. 18-19.

There was one issued in 2017, which was also for the Grand Valley June 19-21.

And in 2008, the only heat advisory for the Front Range and eastern plains was issued Aug. 1-3.

The Pueblo office has never issued a heat advisory.

In 2021, the Grand Junction office issued the first ever Excessive Heat Warning in Colorado which covered the Grand Valley, Paradox Valley, and the Lower Dolores. 

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