Chicago weather: New NOAA data shows climate is warming in Chicago

New data just released by the National Oceanic and Atmospheric Administration shows the climate is warming in Chicago.

Video Transcript

- New data just released by NOAA shows the climate is warming here in Chicago. Every day on ABC7 Eyewitness News, the weather team features the average high and low for the day. Temperatures should be in the upper 60s to right around 70 degrees for this time of year. But look at the forecast, high temperatures only in the 50s.

Well, those averages or normals are based off a 30-year data set. Until recently, that data set was from 1981 to 2010. Starting this week, the new averages are based on data from 1991 to 2020. That 30-year period was warmer than the previous 30-year period. So our averages or normals for Chicago have increased.

Here are some of the notable changes. The average snowfall for Chicago increases 6.1 inches. The old average snowfall for Chicago was 36.3 inches. So the new average becomes 42.4 inches of snow. The average precipitation, which is rainfall plus the water equivalent of snowfall, increased by nearly 4 inches. It's gotten hotter as well in the latest 30-year data set. The average annual temperature has increased 1.5 degrees Fahrenheit.

There are some notable changes in our seasons as well that the new numbers highlight. Spring is markedly wetter. The average precipitation for Spring has increased nearly 2 and 1/2 inches. That's the average precipitation that falls in March, April, and May. In addition to the increase in snowfall as mentioned earlier, the average winter temperature for Chicago has increased 1.2 degrees. But Summer has seen the biggest increase in average temperature.

The new average for summer is 2 degrees hotter. That increase is driven more by warmer overnight lows than daytime highs. And across the nation, the new numbers reveal what we already know. The West is getting hotter and drier. The Eastern half of the country is getting hotter but also wetter. To examine long-term climate change, NOAA looks at the 20th century average compared to the latest 30 years of data.

This map shows the change in precipitation when comparing the 100 years of the 20th century to the past 30 years. The dark green shaded area represents a greater than 10% increase in precipitation. The difference in temperatures is also quite striking. The areas in darker red have seen temperature increases by more than 1 degrees Fahrenheit in the latest 30 years.