July 4-6, 2012 Heat Wave: 2nd Warmest 3-Day Period for Chicago

To put last week’s heat wave in perspective, July 4 through 6, 2012 was officially the second warmest 3 day period in Chicago history, with an average temperature of 91.4 degrees. (Average temperatures are calculated by adding the average high temperature and the average low temperature for the period and dividing by two.) The warmest 3 day average temperature was 91.7 for the period July 28 through July 30, 1916, mainly due to extremely warm overnight lows. In comparison, the July, 1995 heat wave produced a 3 day average temperature of 90.2, which ties for fourth all-time. There were two other times in Chicago history when temperatures reached 100 degrees or higher for 3 straight days – August 4 through 6 of 1947, and July 3 through 5 of 1911. 1911 ties for fourth with July of 1995 at 90.2, but the 1947 3 day average came in at 87. It was not close due to cooler overnight temperatures. The third warmest 3 day period was part of the same 1916 heat wave.

Year	Max/Min	Max/Min	Max/Min	3 Day Average
July 28-30, 1916	99/84	96/85	102/84	91.7
July 4-6, 2012	102/79	103/79	103/82	91.4
July 27-29, 1916	100/82	99/84	96/85	91.0
July 3-5, 1911	100/77	102/78	102/82	90.2
July 13-15, 1995	104/81	100/83	98/75	90.2

July 6, 2012 tied with July 13, 1995 as the second warmest average daily temperature for a single day. July 6, 2012 had a high of 103 and a low of 82 for an average of 92.5. July 13, 1995 had a high of 104, a low of 81, and also an average of 92.5. The warmest day in Chicago history was July 30, 1916. The high was 102 and the low was 84, yielding an average of 93.

Date	Maximum	Minimum	Average
July 30, 1916	102	84	93
July 6, 2012	103	82	92.5
July 13, 1995	104	81	92.5