DES MOINES, Iowa — If your heating bill has been just a little lower in recent years, that may be part of a larger trend.  

Iowa winters haven’t been as cold in recent years compared to, for instance, a hundred years ago. From 1970 to 2023, overnight lows below freezing have decreased by nine nights on average.  

Warmer low temperatures are one way that temperatures have been frequently above average in recent years, especially during wintertime. January and February of this year have followed this trend. January temperatures were 3.9° above normal. Much of that can be seen in the month’s high temperatures. However, you’ll note that several days in January had highs below normal, yet the day was recorded as above average. In these cases, this is because of above-normal overnight low temperatures.  

February has also been off to a mild start, with most days reporting above-average temperatures.  

Iowa State University meteorology professor William Gutowski says he has seen a notable decrease in cold snaps across the state over the last hundred years. While polar outbreaks and cold snaps will still happen, that’s the nature of weather, the air that is coming from the poles is warmer than what is used to be. 

While winters are getting warmer, Gutowski notes that summer temperatures have been slightly cooler. This is partly because Iowa’s air mass is also becoming more moist. Moist air takes more energy to heat up, but it also holds heat more easily. More moisture also leads to more cloud cover, which helps reflect solar energy during the day but hold in heat overnight. 

Gutowski feels this increase in wintertime overnight lows brings a mixed bag. On a positive note, warmer winter weather brings less vulnerability to extreme cold and also requires less energy to heat homes. On the other hand, warmer conditions during wintertime may not kill off as many pests in the winter, which could cause them to arrive earlier in the spring and summer.  

Overall, when it comes to climate, Gutowski says it’s important to look at the bigger picture. That means noticing trends across the country and the world, not just in Iowa, which all contribute to our weather.