Last year in this space, we asked “Whatever happened to the September swoon?” as we noted the fact that Septembers — once the month for a gentle, luscious cooldown as we eased into autumn — have become August 2.0.

Story update for 2024: September was hot. Again. Breaking-records hot for Denver, in fact.

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National Weather Service data shows September’s average temperature (across both the daytime and nighttime) for Denver was 70 degrees. That beats the old record of 69.4 degrees set back in 2015, not even 10 years ago.

Experts suggest the rising average temperatures are a key indicator for climate change in Colorado, as the trend seems to have solidified. Four of the last six Septembers have been the four hottest on record.

These hot Septembers are creating ripples for the environment and for water managers.

"The hot September trend is concerning. It means less natural streamflow in the rivers that provide Denver Water's supply as more water is lost to evaporation and taken up by thirstier plants,” said Nathan Elder, Denver Water’s manager of supply. 

That’s also affecting Denver Water’s collection system. Natural streamflow in September has fallen below the system’s long-term average every year since 2014.

Hot Septembers also mean Denver Water customers are using more water on their landscaping during the month. Since 2017, customers’ outdoor usage during September has been roughly 20% higher compared to September usage between 2000 and 2016.

So, what do we do about it? It’s another reason we make water conservation and efficiency a high priority for the 1.5 million people we serve. 

Oct. 1 marked the end of summer watering rules, so first and foremost it’s time to dial back on the watering and let your lawn and plants prepare for winter dormancy. 

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Better yet, start to think about long-term landscape changes that would reduce your need for higher summer watering. Purchasing a Garden In A Box kit through Resource Central is one great avenue to explore.

Small steps are a perfect way to start, too. There’s no need to tear out all your grass or make giant changes all at once. Taking it slow and learning as you go works too.

You can learn about waterwise plants and landscape transformation on our TAP news site. Try these links for a small sample: Myths and tips about waterwise plants; Five water-wise favorites from Plant Select!; Creating a ColoradoScape.

Meanwhile, we can hope October doesn’t follow September’s hot trend.

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