A Comparison of Chicago and Rockford Heat Waves and Hot Summers

Historic Chicago Heat Waves

Chicago has experienced a number of significant heat waves and hot summers over the years. So how does 2012 compare? Here is a comparison of some of Chicago’s worst hot spells and hottest summers.

Early July Heat Wave 1911

Temperatures hit the century mark three straight days from July 3 through 5 for the first time in Chicago history. This was part of a 5 day hot streak with temperatures above 95.

Late July Heat Wave in 1916

July 26 through July 30, 1916 was arguably the most oppressive period of heat and humidity ever in Chicago. Minimum temperatures were in the 80s for 5 consecutive nights, the longest such string in Chicago history. Warm minimum temperatures are an indication of very high humidity.

1930s Dust Bowl Summers

A series of hot dry summers occurred in the early and mid 1930s. June of 1933 was the hottest June on record for Chicago. The summer of 1936 was the 4th driest on record with only 5.54 inches of rain falling in June, July and August. In the official Chicago record books, the summers of 1934 and 1936 had above normal temperatures but didn't appear to be extremely hot. But these were lakefront temperatures. Inland records from Rockford, Midway and Aurora tell a different story. Many of Rockford's daily record maximum temperatures for the months of May, June, July and August were set in 1934 and still stand today. On May 31 it was 104 at Midway, the earliest 100 temperature recorded at any Chicago area location. Chicago's official all‑time high temperature of 105 (University of Chicago) was set July 24 1934. It was 109 at Midway on July 23, 1934, the highest temperature ever recorded at a Chicago location (but Midway was not the official observatory for Chicago in 1934). July of 1936 produced the longest period of scorching heat ever in northeast Illinois. July 6 through 14 1936 there were 9 days in a row over 100 at Rockford (all records that still stand) and 8 100s in a row at Midway. The hottest day ever in much of northeast Illinois was July 14 1936. The high temperature was 112 at Rockford, 111 at Aurora and 104 at Midway.

August 1947 Heat Wave

June and July of 1947 featured below normal temperatures, but August was sizzling. The average temperature of 80.2 makes it the hottest August on record. There were 4 days of 100 or greater, including three in a row, and five other days with a temperature of at least 97. .

The Hot Summers of the 1950s

There were 4 consecutive hot summers beginning in 1952. The heat peaked in 1955, Chicago’s all‑time warmest summer (1952 was the 12th warmest, 1953 was 7th and 1954 was 9th). July 1955 was the warmest month on record with an average temperature of 81.3. Summer of 1955 had 46 days with a temperature of 90 or greater, including a record 11 in a row from July 26 through August 5. (The summers of 1953 and 1954 also had 11 straight days of 90 weather) this period also had 10 straight minimum temperatures of 75 or greater. This had to be the longest period of very oppressive heat and humidity in Chicago history.

The Hot Dry Summer of 1988

There were 47 days with temperatures in the 90s and 7 days in the 100s, both records. Drought led to lower humidity and lower minimum temperatures than other hot summers. So, despite all the 90 and 100 days, 1988 ended up only the 10th warmest summer.

The Deadly Summer of 1995

Around 600 people died in the mid July heat wave, making this the deadliest weather event in Chicago history. Humidity was extremely high with dew point temperatures in the upper 70s to lower 80s. The hottest day was July 13. The high of 104 at O’Hare (official Chicago observatory) was the second highest official temperature in Chicago. The temperature reached 106 at Midway and 103 at Meigs Field. The heat index peaked at 119 at O’Hare and 125 at Midway. This was probably the most intense combination of heat and humidity ever in Chicago. The summer of 1995 was the second warmest on record.

A Few of Chicago’s Worst Heat Waves

* Chicago all-time record high maximum temperature105 July 24, 1934

** Chicago all-time record high minimum temperature 85 July 29, 1916

Historic Rockford Heat Waves

When it comes to Rockford’s heat waves, one event stands head and shoulders above any other. That was the torrid July of 1936. Several other intense hot spells occurred, mainly between 1916 and 1947.

1916

There was a heat wave in late July with nine straight days of at least 95 degree heat, including four days in a row over 100 degrees. It was the fourth warmest July on record. The temperature hit 100 three more times in August.

July 23	July 24	July 25	July 26	July 27	July 28	July 29	July 30	July31
96	95	95	98	99	103	104	104	105

1921

The summer of 1921 was the hottest on record for Rockford. It produced the warmest July and third warmest June ever. While June didn’t produce any extreme temperatures, it was in the 90s sixteen days. Temperatures were 95 or greater on eleven of the first thirteen days of July, reaching 100 on five days.

1931

Late June and early July produced an intense heat wave. There were seven straight days with temperatures 99 or greater

Jun 25	Jun 26	Jun 27	Jun 28	Jun 29	Jun 30	July 1
99	100	99	100	103	102	101

1934

The heat came early and often. It was 95 degrees on May 6. Temperatures climbed above 90 ten times in May including 106 on May 31. Rockford’s earliest intense heat wave on record was May 29 through June 4 with temperatures in the upper 90s to low 100s.

May 29	May 30	May 31	June 1	June 2	June 3	June 4
97	96	106	106	98	100	98

The heat continued through June with a total of seventeen days above 90 and three days over 100. June of 1934 was the second warmest on record and the summer of 1934 was the second warmest on record. Another very intense heat wave occurred in mid to late July with a string of six days over 100.

July 19	20	21	22	23	24	25	26
96	101	102	104	104	107	105	97

There was one more 100 degree temperature in early August

1936

June was near normal with only four days in the 90s. But things changed dramatically in early July. The most intense heat wave in Rockford’s history began July 6 and continued through July 18. This heat wave produced 11 days over 100 degrees, including nine in a row, and Rockford’s all-time high temperature of 112 on July 14.

Jul 6	Jul 7	Jul 8	Jul 9	Jul 10	Jul 11	Jul 12	Jul 13	Jul 14	Jul 15	Jul 16	Jul 17	Jul 18
102	105	104	101	106	108	109	110	112	99	100	104	95

1947

August of 1947 was the hottest August on record. The worst stretch was from the 17th through the 24th, which featured five days of 100 or greater.

Aug 17	Aug 18	Aug 19	Aug 20	Aug 21	Aug 22	Aug 23	Aug 24
98	100	100	100	98	99	101	102

2012

The present heat wave is likely the most intense heat wave Rockford has experienced since 1947 or 1953.

July 2	July 3	July 4	July 5	July 6	July 7
98	97	102	102	104	105

Year	Month/Day Min/Max	Month/Day Min/Max	Month/Day Min/Max	Month/Day Min/Max	Month/Day Min/Max
1911	7/1 75/96	7/2 79/98	7/3 77/100	7/4 78/102	7/5 82/102
1916	7/26 80/89	7/27 82/100	7/28 84/99	7/29 85**/96	7/30 84/102
1934	7/21 75/95	7/22 76/101	7/23 75/94	7/24 78/105*	7/25 76/93
1947	8/3 71/91	8/4 71/100	8/5 75/100	8/6 75/101
1988	8/1 78/100	8/2 79/100	8/3 80/96	8/4 78/97
1995	7/12 73/97	7/13 81/104	7/14 83/100	7/15 75/98	7/16 74/93
2012	7/2 71/98	7/3 77/96	7/4 79/102	7/5 79/103	7/6 82/103