Tuesday Sept. 26 2017 Marked the 7th Consecutive Record High Temperature in Chicago

September 2017 marks the only occurrence on record for Chicago of a seven-day period of consecutive 90°F-plus days entirely within September. The first record high day was Wednesday, September 20, 2017. The record warmth continued every day through Tuesday September 26, 2017. The temperatures were about 20 degrees above normal, ranging from 92°F to 95°F..

RECENT RECORD HIGHS O’HARE (OFFICIAL)

Record High 92°F
Tuesday Sept. 26, 2017 1:38 PM

Record High 92°F
Monday Sept. 25, 2017 1:53 PM

Record High 93°F
Sunday Sept. 24, 2017 1:57 PM

Record High 95°F
Saturday Sept. 23, 2017 12:41 PM

Record High 94°F
Friday Sept. 22, 2017 3:41 PM

Record High 94°F
Thursday Sept. 21, 2017 3:27 PM

Record High 92°F
Wednesday September 20, 2017 3:29 PM

Have There Been This Many Consecutive Record Days Before?
At Chicago’s official National Weather Service station at O’Hare International Airport, record high temperatures occurred during a nine-day period in March 2012 from March 14, 2012 through March 22, 2012 with record temperatures in the 80s and upper 70s (ranging from 78 to 87). The record temperatures were 30 to 38 degrees above normal. Record warm low temperatures occurred on March 7, March 17, March 19, March 20, March 21, March 22, and March 23. Even with the lake water temperatures in the 30s, the chilling effect of lake winds did not occur in March 2012.

The record warm March 2012 temperatures were preceded by an extraordinarily warm October 2011 from October 4, 2011 through October 12, 2011. No record highs were broken during the October 2011 period, but temperatures were in the upper 70s and 80s (about 10 to almost 20 degrees above normal) for the nine-day period.

The most recent stretch of 92°F plus days occurred from July 27, 1988 through August 4, 1988 — a duration of nine days.

What Caused the Record Late September Warmth?
A massive upper ridge with sunshine sat over the eastern United States

The jet stream over western Texas, western Oklahoma, western Kansas, Nebraska, South Dakota, and Minnesota kept weather systems and rain over the Rockies region, while southerly flow brought warm air from the Gulf over the Midwest and eastern United States.

Persistent dryness with lack of significant rain results in more efficient warming of the soil surface.

The blocked pattern caused by the jet stream was enhanced by the action of multiple hurricanes pushing warm Gulf air to the north.

Is there More Warmth Expected in October 2017
The Climate Prediction Center has published “Above Normal Warmth Likely” for the 6-10 Day Temperatures Outlook and the 8-14 Day Temperature Outlook.

Depending on cloud cover and the persistence of dry weather conditions, afternoon temperatures in the 80s are possible for the first half of October 2017. Maximum sunshine and dry conditions could produce temperatures in the 90s in October. The latest 90s temperature recorded in Chicago occurred October 6, 1963.

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 RECENT ALERTS … 

Past NWS Chicago alerts during the September 2017 Heat Wave.