2024 Weather Was Very Warm and Wild

Illinois was both warmer and wetter than the 1991–2020 normal in 2024. The statewide average annual temperature was 55.5 degrees, 2.9 degrees above normal and 2nd warmest on record statewide. Statewide average total precipitation in 2024 was 40.69 inches, 0.05 inches above normal and the 43rd wettest year on record.

The Second Warmest Year on Record

The past year was very warm in Illinois, but the largest temperature departures from normal were outside of the climatologically warmest time of the year. February, March, and November were all at least 4 degrees warmer than normal, while July and August were near to slightly cooler than normal statewide (Figure 1).  

Figure 1. Plot shows 2023 statewide monthly average temperature (black line) and temperature departures from the 1991–2020 normal (red and blue bars).

Average temperatures in Illinois last year ranged from the low 50s in northern Illinois to the low 60s in southern Illinois, between 1 and 6 degrees above normal (Figure 2). The year 2024 was the warmest year on record in Chicago, Peoria, St. Louis, and Paducah, and it was a top 5 warmest year on record in the Quad Cities, Champaign-Urbana, Quincy, and Carbondale, among other places. The warmest point in the state last year was Dixon Springs in Pope County with an average temperature of 60.2 degrees. The coolest point in the state was Stockton in Jo Daviess County with an average temperature of 50.2 degrees.

Figure 2. Maps show 2024 annual average temperature (left) and average temperature departures from the 1991–2020 normal (right).

Last year was the warmest on record in Chicago, which stretches back to the 1870s. The weather station of record for the city of Chicago is currently at O’Hare airport; however, the station’s location has changed multiple times since the 1870s. For the first half of the record, the station was much closer to Lake Michigan, including in the Roanoke Building between 1873 and 1887 and Rosenwald Hall at the University of Chicago between 1926 and 1942. The Chicago National Weather Service office has a complete weather history for Chicago and Rockford: https://www.weather.gov/lot/observation_history.

Despite the likely moderating effect of the lake on temperatures in the early part of Chicago’s record, 2024 was still the warmest year since Ulysses Grant was president. Figure 3 shows the record of annual average temperature in Chicago, illustrating a long-term warming trend the city has experienced over the past 150 years.

Figure 3. Plot shows the annual average temperature in Chicago from 1873 to 2024.

Table 1 shows the number of daily weather records broken at Illinois Cooperative Observer stations in each month of 2024.

Our very mild February led with the highest number of daily high maximum temperature records, with 222 statewide. Meanwhile, the final three months of the year led with the most high minimum temperature records with 101, 67, and 64, respectively. The fleeting but intense cold air outbreak in mid-January in 2024 broke 73 low maximum temperature records and 28 low minimum temperature records. Multiple months had at least 100 daily high precipitation records broken last month, including January, April, July, and November.

Table 1. Table shows the number of daily local weather records in 2023 by month and variable.

2024 Precipitation

Calendar year 2024 had quite variable precipitation, with five months of wetter than normal conditions (January, April, July, November, December) and seven months that were drier than normal (Figure 4).

Figure 4. 2024 monthly total precipitation as a departure from the 1991–2020 normal.

Illinois experienced the 2nd driest February on record statewide, with only 0.48 inches of statewide average February precipitation, about 1.5 inches below normal. A wetter than normal April and May helped refill soils ahead of the growing season, but also delayed crop planting and critical fieldwork in many parts of the state.

July brought multiple rounds of heavy rain to the state, including events that caused widespread damaging flooding in the St. Louis Metro East area: https://storymaps.arcgis.com/stories/df7ac819701a445399d7fe87328b4f77, and the Rockford area: https://www.weather.gov/lot/2024_07_13-14_Flooding. Nashville, Illinois experienced over 6 inches of rain in less than 8 hours on July 16th, forcing overflow of a local reservoir and flooding of several homes.  

For the third consecutive year Illinois fell back into drought in the fall as the months of September and October were 1 to 3 inches drier than normal across the state. Total precipitation in September and October statewide was only 3.48 inches, about 60% of normal and the 12th driest 2-month period on record. Once again, the region’s largest rivers approached low stage, including along the Illinois, Mississippi, and Ohio Rivers, causing some moderate challenges to shipping. November and December were both wetter than normal to end the year.

Figure 5 shows the spatial variability of 2024 precipitation in more detail. Total precipitation last year ranged from over 60 inches in far southern Illinois and the St. Louis Metro East area to less than 35 inches in parts of northern and north-central Illinois. Areas along the Wisconsin and Iowa borders were 2 to 6 inches wetter than normal last year, and areas around St. Louis and along the Interstate 70 corridor were 6 to 12 inches wetter than normal.

Figure 5. Maps show (left) total precipitation and (right) precipitation departures in 2024.

A CoCoRaHS citizen science observer in Metropolis in Massac County had 62.92 inches of precipitation in 2024, making the birth of Superman the wettest point in the state. Meanwhile, another CoCoRaHS observer in El Paso in Woodford County had only 28.22 inches of precipitation in 2024.

Overall, statewide average total precipitation in 2024 was 40.69 inches, 0.05 inches above normal and the 43rd wettest year on record.

2024 Severe Weather

Severe weather came early and often in 2024, with all of our 102 counties affected by strong wind, hail, tornadoes, or heavy rain (Figure 6). Overall, the NOAA Storm Prediction Center reported a preliminary 142 tornadoes in Illinois in 2024, which  would set a new annual tornado record, breaking the 124 event record in 2006, and follows the very active tornado year of 2023 with 121 tornadoes. Figure 6 shows the monthly frequency of tornadoes in 2024 compared to the 1994-2023 average frequency. February through May had above average tornado frequency, and then came a record-breaking July. The 7th month of the year ended with 45 tornadoes in the state, including a massive tornado outbreak in the Chicagoland area on July 15th. In total, the derecho on that evening brought 32 confirmed tornadoes, including several that made it into the Chicago city limits: https://www.weather.gov/lot/2024_07_15_Derecho.  

Only one tornado was reported in the last four months of the year. It is likely the 2024 tornado total will be adjusted, but irrespective of changes, 2024 was an extremely active tornado year and very likely the most active tornado year on record in Illinois

Figure 6. Plot shows tornado frequency by month in 2024 (blue bars) compared to the 1994-2023 average (red bars).

The NOAA Storm Prediction Center also had 216 severe hail reports and 716 severe wind reports in Illinois in 2024. Many of the wind reports came from a strong derecho that moved through the state on June 29. Over one-third of all severe wind reports came on July 15th, including 100+ mph wind reports in Marshall County and Ogle County.

2024 Snowfall

Snow was hard to come by in 2024. Figure 7 shows snowfall departures from normal between January and May, September and December, and for the 2024 year as a whole. Most places in the state had between 5 and 20 inches below normal snowfall last year. Overall, the statewide average total snowfall was just under 12 inches in 2024, below the long term average of 19 inches (Figure 7).

Figure 7. Maps of snowfall departures from normal across Illinois and a plot of statewide average total snowfall in Illinois between 1904 and 2024. The maps show departures from (left) January through May, (middle) September through December, and (right) the entire year of 2024.

National Climate Assessment for Illinois

Earlier this year the National Climate Assessment for Illinois was released, tracking the historical changes in temperatures and precipitation in Illinois. You can find the full report for Illinois and other states at the State Climate Summaries website.
Here is Key Message #1

Average annual temperature has increased by about 1°F since the beginning of the 20th century. There has been seasonal variation in this warming, with average spring temperature increasing by about 2°F and average summer
temperature increasing very little. Under a higher emissions pathway, historically unprecedented warming is projected by the end of the 21st century.

Key Message #2

Precipitation in spring and summer has generally been above average over the past two decades, affecting agriculture in both positive (adequate soil moisture) and negative (delays in spring planting) ways. Precipitation in winter and spring is projected to increase, which poses a continuing risk of spring planting delays.

Key Message #3

Severe flooding and drought have occurred periodically in recent years. Future increases in extreme precipitation events and in evaporation rates may increase the intensity of both floods and droughts.

You may notice that two out of the three messages relate to increases in precipitation and especially heavy rainfall events. The graphic I found most compelling was this one for the increasing number of 2-inch rain events with time. The caption explains how this graph was created. The increased frequency in 2-inch rain events seen since the early 1980s lines up very well with my experience and research over the years in Illinois.

il_obs-number-extreme-precip_v1_2
Figure 5: The observed number of days with extreme precipitation events (annual number of days with precipitation greater than 2 inches) for 1900–2014, averaged over 5-year periods; these values are averages from 43 available long-term reporting stations. A typical station experiences 1–2 such events each year. The number of extreme precipitation events has been above average since the 1990s. During the most recent 5-year period (2010–2014), Illinois experienced a record high number of events when stations averaged more than 2 events annually. The dark horizontal line is the long-term average (1900–2014) of 1.62 days per year. Source: CICS-NC and NOAA NCEI.

Continue reading “National Climate Assessment for Illinois”

Volcanoes and Climate in Illinois

When I give talks on climate and climate change, I often get questions about volcanoes and their impact on our climate. The Washington Post had a recent article on the subject, mentioning the famous eruption of Tambora in 1815, which in 1816 led to the year without a summer in the eastern US. It probably had impacts on Illinois but we had no widespread observations in place at the time.

http://www.washingtonpost.com/blogs/capital-weather-gang/wp/2015/04/24/the-epic-volcano-eruption-that-led-to-the-year-without-a-summer/

The one I remember the best was Mount Pinatubo. The following summer after that eruption was exceptionally cool across the US and around the world.

summer1992
Summer 1992 temperature departures from average for the lower 48 states. Shades of green indicate level of coolness. Click to enlarge.

Continue reading “Volcanoes and Climate in Illinois”

2014 – Warmest on Record for World, 6th Coldest for Illinois. Wait, What?

I could see this one coming. While Illinois had its 6th coldest year on record, three major groups (Japan, NASA, and NOAA) have noted that 2014 was the warmest year on record. Check out this map from NOAA of the temperature departures for 2014 (red is warmer, blue is cooler). The area from the Great Lakes and southward to the Gulf of Mexico was the only place over land that was colder than average. All the other land masses and most of the ocean surface was warmer than average. In other words, relatively speaking, Illinois was one of the coldest places on earth in 2014.  Continue reading “2014 – Warmest on Record for World, 6th Coldest for Illinois. Wait, What?”