From Record Heat to Frost

The Midwest, 12–17 October 2026

On Monday Chicago reached 88° at O'Hare, 24 degrees above normal and 4 above the old record for the date. In the station's record since 1872, only 3 other days this late in the year have been as hot: 15 October 1947, and 13 and 14 October 1975. Across the region, 20 of 67 long-record NOAA stations set a record high for 12 October and 6 more tied one. Then the cold front. By Saturday morning the forecast puts 17 of those 26 places at 36° or colder, cold enough for frost, and 8 at freezing or below.

What happened

Chicago, O'Haredaily high and low, °F; dashed = NWS forecast

88° on 12 Oct, the normal high 64°. Shaded: the normal range, 1991–2020. The forecast is NWS Chicago's, issued 00:11 UTC 14 Oct; 13 Oct had not been reported when the map was made, hence the gap.

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Sources. Monday's high: NOAA URMA 2.5 km hourly analyses of 2 m temperature (24 hours, midnight to midnight CDT), highest hour per cell; bands traced from the lightly smoothed grids (generalized). Saturday's low: NWS National Digital Forecast Database MinT valid 12Z 17 October 2026, issued 00Z 14 October 2026 (a forecast). Records and normals (1991–2020): NOAA RCC ACIS, ThreadEx long-term stations (67 in these states with a 12 Oct report); Chicago = O'Hare ThreadEx, record from 12 June 1872. Forecast for Chicago: NWS Chicago, api.weather.gov. Hourly grids can run a degree or two under a station's peak; the station numbers are the official ones. Lakes: Natural Earth. Figures provisional. Web Mercator; the printed map is Albers equal-area conic.