I think it’s safe to say that’s it’s been pretty hot lately across Colorado. This is not super atypical though. Colorado, especially the eastern Plains and western Canyons and valleys, get very hot this time of the year.

What’s becoming increasingly more noticeable is that the heat seems to last for a longer period of time and overnight, we’re not cooling off as normal.

That’s the point of this post. Nights are warming at a quick rate. Although we don’t have the blaring sun during the nighttime hours, warm overnight temperatures make your body work harder to cool itself putting stress on heat-sensitive populations that don’t have access to reliable A/C or cooling centers. Also, warm nights allow for temperatures to rise more quickly during the morning hours. I’m sure you’ve noticed the warmth at 7/8 am and the 90º readings by 10am. While not unheard of for this area, the number of times this happens per season is increasing.

Let’s dive into the numbers.

Warming Summer Nights

Data compiled by Climate Central is referencing meteorological summer which runs from June 1 to August 31.

Grand Junction, Colorado Springs and Denver have all seen increases in their respective overnight low temperatures.

For Grand Junction, the change is not as steep as it is in Denver and Colorado Springs but western Colorado is still seeing a slight increase in overnight average temps. Colorado Springs and Denver are closing in on feeling close to a +2º change in overnight temps.

For Denver that means that some nights the temperatures won’t dip below 70º. It’s already happened 3 times this summer season and could be a more common occurrence going forward.

Nights where temperatures stay at or above 70º is rare. Other than this year, there are only 3 summers in our 140+ year weather history where there were more 70º nights than this years.

We’ve talked a lot about warm nights but warm nights usually lead to hot days. The number of hot days (or days above 90-100º (depending on the city)) has increased as well over the last 50 years.

Again, Grand Junction is seeing an increase in hot weather but not as dramatic as the eastern side of the state. Also note that this map measures Grand Junctions number of 100º days. Denver’s number of 95º days and Colorado Springs number of 90º days are increasing by 17-19 more days than in 1970.

What probably goes without saying is that with warmer nights and more hot days, our general summer temperatures are rising. Region-wide, Colorado is seeing a warming trend across all hours of the day in the summer months.

Grand Junction has seen an increase in summer temperatures of around 1º whereas Denver and Colorado Springs have seen summer temperatures increase by 2.6º.

So, if you’ve been thinking that the last few summers – or the last few decades – have been a bit warmer than you’re used to, you’re not wrong. We’re seeing a warming trend across the board in Colorado during the summer months.

Looking at what has happened this year already, the data proves the this case well.

For July, there are many “hot spots” where average nighttime temperatures are running well above normal. Going back from the start of June, that still stands true. Our average nightly temperatures during this meteorological summer (which runs from June through August) are running well above normal statewide.

Heat advisories will become a big more common over the coming years due to a change regarding when to issue advisories. Heat advisories used to be issued when temperatures, or duration of heat met a certain threshold. Living in a dry, high dessert environment like most Coloradans do, meeting temperature thresholds is just not easy to do because of the lack of humidity and how efficient grass and dirt areas cool off at night. Instead, heat advisories will be issued based on impacts to the population. Find the Heat Risk map here. This has become evident this year as the most heat advisories ever have been issued.

This should now be updated to 7 for this year since we are currently (Friday, July 22) under a heat advisory in NE Colorado

Prior to this year, 2008 held the title for most heat advisories. Now, with the change from threshold based to impact based, we are and will continue to see more heat advisories issued across the state – especially in highly populated areas.

Something to think about: A lot of this heat is lasting longer into the fall season as well. I’m sure you’ve heard of summer lasting longer and that’s true for much of Colorado. That’s not to see we can’t have early-season cold blasts but those are becoming increasing more uncommon. I’ll update you on the lengthening of the summer season in a few weeks.


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