Why are the lows so high in Utah?

You read that right. On Monday, the National Weather Service reported that the temperature was a whopping 86 degrees at 6 a.m. at the weather station at Salt Lake City International Airport. That would have been the highest low in recorded SLC history before it dipped that night to “just” 82 degrees at 10:30 p.m. — tying the all-time record.

Regular readers of this column will remember that higher low temperatures have been a trend at Salt Lake’s airport — and no, not because of a conspiracy theory to set the thermometer higher. Indeed, while weather has been warming overall in recent years, it’s the winter and nighttime temperatures that have increased most, the NWS told me.

So what’s going on? Why are the lows so high in particular?

What has caused our nights to be so warm?

To answer this question, I talked to David Church, Science and Operations Officer at the National Weather Service Salt Lake City office.

“At night, for conditions to cool off, all that heat accumulated at the surface during the daytime must escape back into space, and anything that prevents this process leads to warmer overnight low temperatures,” Church explained.

What are some of those factors that stop heat from escaping at night?

First, cloud cover. There is an oft-used analogy that clouds act like a blanket at night, and the analogy basically works. In reality, clouds are water vapor, and any kind of water vapor and moisture in the atmosphere works to absorb some heat trying to leave the surface and radiate it back to the ground.

Both factors were at play on Monday. “We had thick cloud cover overnight that moved in quickly just in time for sunset and persisted through the night,” Church told me. One measure of atmospheric water vapor is called precipitable water, and the NWS’s 6 p.m. weather balloon observed a precipitable water value of 1.22 inches. The median precipitable water for late July is around .6 to .7 inches, so the reading well exceeded the norm.

In addition, winds can help keep nighttime lows high. Without winds, heat naturally rises, creating sort of an inversion effect at night similar to what the valley experiences during winters — cold air down below, warm air on top. But winds can disrupt the inversion, pushing some of the warmer air back down to the surface.

And sure enough, on Sunday night, “Winds remained persistently breezy overnight from the south, generally around 10-20 mph with occasional gusts to around 30 mph.”

That — plus the obvious reality that the day itself was very hot, 8 degrees above the normal average — was the perfect storm for setting a record high of a low.

Other weather trends this summer

Beyond the record highs and lows, how else can we sum up this summer’s weather?

To find out, I decided to look at the data from 30 Utah weather stations — 18 of them within the Wasatch Front. I compared the weather from June 1 through July 24 for all 30 stations, and compared it to the same period over the last 30 years before 2026.

This summer, so far, has been quite warm, quite dry, and not very windy overall. While we have seen some record highs, there have been a few warmer summers overall: 2017, 2021, and 2024.

Being selfishly interested in weather where I live, I also wanted to look at the same information for Salt Lake City in particular.

Those high lows become prominent here, as is the relative lack of wind. But again, overall, this hasn’t been Salt Lake City’s warmest summer.

However, the heat isn’t going away soon. This week, the forecast models currently show “anomalously high temperatures” this weekend, with highs between 103 on Friday and 105 on Saturday expected at the Salt Lake City airport. This is thanks to a large, dry air mass moving toward Utah, with moisture remaining well to the west.

Lows are expected to be more normal, though, in the mid-70s. Maybe, just maybe, your air conditioners can get a short break.