O'Hare runs 1.5°F warmer than normal over the past 24 months

The warm stretch many Chicagoans have felt is real. At O'Hare International Airport on the Northwest Side, the average month over the past 24 months ran 1.5°F warmer than its 1991–2020 normal.

Rain and snow tell a different story. Total precipitation at O'Hare came in below normal over the same period, even though a few months were far wetter than usual. The newest monthly summaries run through September 2026.

Those patterns matter at home. Warm months shift what households spend on heating and cooling, change what gardeners can plant and when, and shape how cities and homeowners plan for heavy rain.

A warm run, month after month

From October 2024 through September 2026, O'Hare's mean monthly temperature was 52.8°F. The 1991–2020 normals for those same calendar months average 51.3°F.

The warmth was spread across the calendar, not packed into a short burst. Of the 24 months we checked, 16 months came in warmer than normal for that time of year. Warm months outnumbered cool ones by a wide margin.

The chart below plots each month's average temperature against the normal for that calendar month. Months above the normal line ran warm; months below it ran cool.

The biggest swings were warm ones. The month with the largest temperature departure ran 5.7°F above its normal. The next-largest departure was 5.5°F above normal.

Those are large gaps for a monthly average, which smooths out hot and cold days alike. A month that lands that far from normal usually means many days ran warm, not just a few.

The chart below shows every month's departure from normal and highlights the months with the largest swings in either direction.

The National Weather Service's Chicago office publishes its own monthly summaries. In one recent summary, it reported the month's mean temperature and how far above normal it landed (weather.gov). Our figures use the same kind of month-by-month comparison across the full period.

When a warm month falls matters for household budgets. A mild winter month generally means less need for heat, while a hot summer month means more air conditioning. The averages here do not show which bills rose or fell for any family.

Drier overall, with wet spikes

O'Hare recorded 71.3 inches of precipitation, counting rain and melted snow, over the past 24 months. Normals for those months add up to 75.7 inches.

That puts the period's total departure at -4.4 inches. In plain terms, Chicagoland's main weather station came in drier than normal over the full stretch.

Wet months were in the minority. Only 11 months out of 24 months brought more precipitation than normal for that time of year.

But the wet months could be very wet. The month with the largest rain departure recorded 7.2 inches of precipitation, a departure of 3.5 inches above its normal.

Dry months swung hard the other way. The next-largest rain departure was -3.3 inches, a month that left lawns and gardens well short of their usual water.

Monthly totals can also hide soaking days. The weather service's Chicago office notes daily rainfall records in its monthly reports, including a record daily liquid precipitation total on one day of a recent month (weather.gov).

That is the kind of event that tests storm sewers and basements. A period can run drier than normal overall and still deliver downpours that flood streets and yards.

What to watch

The figures describe what happened at O'Hare. They do not explain why the past 24 months ran warm or why rain came in uneven bursts, and this analysis does not try to assign a reason.

Conditions also vary across the region. Neighborhoods near the lake, in the Loop or on the South Side, and suburbs to the west and south, can see different temperatures and rain totals than the airport does.

Readers can watch a few things as autumn turns to winter:

• Whether the October 2026 summary keeps the warm streak going or breaks it.
• How the coming winter months compare with normal, which will matter for heating bills.
• Whether the dry tilt in total precipitation continues, or a wet stretch closes the gap with normal.
• Heavy downpours on individual days, which monthly totals can mask but which matter most for flood planning.

For now, the record at O'Hare is clear on temperature. The past 24 months ran warmer than the 1991–2020 baseline far more often than not, and the most extreme months ran warm.

How we did this

We compared O'Hare's monthly average temperature and total precipitation for October 2024 through September 2026 with the 1991–2020 normal for each calendar month. We averaged the monthly temperature departures across all 24 months, counted months above normal, and compared total observed precipitation (71.3 inches) with the sum of the monthly normals (75.7 inches). We then ranked months by the size of their departure from normal.

Normal: the average value for a given calendar month over 1991 through 2020, used as a baseline for comparison. Departure from normal: how far a month's observed temperature or precipitation landed above (positive) or below (negative) its normal. Precipitation: rain plus the water content of melted snow and ice, measured in inches. Monthly average temperature: the average of daily temperatures over a month, which smooths out individual hot and cold days.

Limitations

• The data come from a single weather station at O'Hare. Temperatures and rainfall in other parts of Chicago and the suburbs can differ.
• The most recent months may be preliminary and could be revised after quality checks.
• Monthly averages and totals hide daily extremes, such as a heat wave or a downpour on one day.
• The data show how weather compared with normal, not why. This analysis does not identify causes.
• We did not compare Chicago with other metro areas over the same period.
• Normals are a 1991–2020 average for each calendar month, not a forecast or a guarantee of what a typical month will bring.

Sources

• NOAA National Centers for Environmental Information: Monthly weather summary (Global Summary of the Month): USW00094846, latest period September 2026; retrieved Oct. 15, 2026. Data
• NOAA National Centers for Environmental Information: Monthly climate normals, 1991–2020: USW00094846 (1991–2020 U.S. Climate Normals), latest period 2020; retrieved Oct. 14, 2026. Data