Summary of July 1-7 Wisconsin Heat Wave (Updated 4 pm 7/23)

...Updated fatality information in 1st paragraph...

Wisconsin experienced a major heat wave during the first 7 days of July 2012, peaking July 4-6th.  There were several heat-related fatalities during this event and mostly likely several hundred people needed medical treatment.   As of Monday, July 23rd, there were 10 confirmed heat-related fatalities: two in Barron County, two in La Crosse County, and one in each of the following counties: Dane, Juneau, Kewaunee, Richland, Rock County, andVernon.  Additionally, there are other fatalities are under investigation to see if they are heat-related. 

The July 2012 heat wave was roughly as hot as the killer July 1995 heat wave, but less humid and longer in duration. Maximum air temperatures in the July 2012 heat wave ranged from the upper 90s to 106 degrees. However, it was cooler near Lake Michigan and Lake Superior and across parts of northern one-third of Wisconsin. Maximum heat indices (apparent temperature) peaked in the 100 to 115 range thanks to dewpoints reaching the mid-60s to mid-70s.

Dry soils across southern Wisconsin allowed for deeper mixing of the lower atmosphere due to daytime heating which brought drier down to the ground.  Consequently, relative humidities and heat indices during the July 1-7 heat wave were lower than those experienced in the July 1995 heat wave.  Information on the July, 1995 killer heat wave can be found here.

Numerous daily record maximum temperatures were tied or broken during the heat wave, as well as new record high minimum temperatures.  Details on these records are found toward the bottom of this summary.

Characteristics and impacts of the July 2012 heat wave that stand out:

  • Fatalities (10 confirmed heat-related and possibly others under investigation) & possibly several hundred injuries (sought medical treatment)
  • Buckled and cracked road surfaces
  • Isolated bird & fish deaths, and possibly some pet and livestock/animal losses (assumption based on history)
  • Maximum air temperatures – 100 to 106.
  • Maximum heat indices of 100 to 115 (they were 118 to 128 in July 1995).
  • Dew-points in the mid 60s to mid 70s (they were in the upper 70s to lower 80s in July 1995).
  • Stuffy overnight minimum temperatures in the 70s to lower 80s.
  • Little or no rain.
  • Unusual long duration (7 days), not to mention a couple hot days centered on June 28th.
  • Drought conditions intensified across southern Wisconsin to moderate levels.
  • A few minor wildfire-grass-tree burns in southern counties.
  • Many cities and Civil Townships banned outdoor burning and fireworks.
  • Crops, trees, shrubs, lawns showing water & heat stress.
  • Some ponds, marshes, and small streams have dried up (water table probably lowering?)

The heat wave was generated by a large, warm, high pressure in the mid to upper levels of the atmosphere stretching from the Kansas area east to the Ohio River Valley. Sinking air in the high pressure warmed and formed a “cap” that resulted in more sunshine than usual and hot temperatures.

The Midwest Picture

In the first row below are 4 images for the Midwest for July 1-8th, left to right, showing the average temperature, the temperature departure, precipitation, and the percentage of normal precipitation.  These images were generated by the Midwest Regional Climate Center (MRCC).  Note the greatest temperature and precipitation anomalies are located from northeastern Iowa and southeastern Minnesota across southern Wisconsin!  Click on thumbnail for larger version.

midwest avg temp July 1-8   Midwest avg temp  midwest pcpn  midwest pcpn departure

Below are images showing maximum air temperature contours across the Midwest for July 1-8th.  Click on thumbnail for larger version.

July 1 temps midwest  July 2 temps midwest  July 3 temps midwest July 4 temps midwest

July 5 temps midwest  July 6 Max Temps Midwest  July 7 Max Temps Midwest  July 8 Max Temps Midwest

Wisconsin - Maximum Air Temperatures

Below are daily maximum air temperatures at selected cities across the state, followed by the locations that had the highest daily temperature through the period.  Note:  "AP" is an abbreviation for "Airport." 

Wisconsin Cities 
July 1st
July 2nd
July 3rd
July 4th
July 5th
July 6th
July 7th
Superior
79
73
90
73
88
70
84
Eau Claire
92
99
92
98
94
99
85
Rhinelander
83
91
90
91
92
87
79
Wausau
85
95
91
95
96
96
85 
Green Bay AP
90
92
91
95
99
95
82
Appleton
88
91
91
93
97
93
81
La Crosse AP
94
99
99
103
98
103
86
Boscobel AP
98
102
99
103
102
105
94
Fond du Lac AP
91
94
95
100
101
99
81
Sheboygan AP
88
86
93
97
102
93
81
Madison AP
95
97
96
102
104
102
89
NWS Sullivan (MKX) 
96
99
100
105
106
105
92
Waukesha AP
90
93
93
100
100
100
82
Milwaukee AP
84
87
97
102
103
94
86
Janesville AP
95
100
99
104
104
106
99
Racine AP
87
88
98
104
102
95
83
 Kenosha AP
92
93
99
105
106
102
84
State Max Temp
Boscobel AP
98
102
 
 
 
 
 
State Max Temp
Wautoma
 
 
101
 
 
 
 
State Max Temp
NWS Sullivan (MKX)
Kenosha AP
Paddock Lake
Wautoma
 
 
 
105
 
 
 
State Max Temp
Kenosha AP
NWS Sullivan (MKX)
Middleton AP
Wautoma
 
 
 
 
106
 
 
State Max Temp
Janesville AP
Paddock Lake
 
 
 
 
 
106
 
State Max Temp
Darlington
 
 
 
 
 
 
102

Below are images showing daily maximum temperatures across Wisconsin during the heat wave.  Click on thumbnail for larger version.

July max tmeps WI  July 2 max temps WI  July 3 max temps WI

July 4 max temps WI  July 5 max temps WI  July 6 mx temps WI  July 7 max temps WI

Wisconsin - Maximum Heat Indices (Apparent Temperature)

Below are images showing daily maximum heat indices (apparent temperatures) across Wisconsin during the heat wave.  Click on thumbnail for larger version.

July 1 HI WI  July 2 HI WI  July 3 HI WI

July 4 HI WI  July 5 HI WI  July 6 HI WI  July 7 HI WI

Milwaukee and Madison Hourly Heat Indices (Apparent Temperature)

Below are two line graphs depicting the hourly heat indices at the airports in Milwaukee and Madison.  Note the rapid rise in the mid-morning hours, and in some cases, a slight increase in the 7 to 8 pm CDT timeframe once the boundary layer of the atmosphere "decouples" from the rest of the atmosphere.  When this happens a low-level inversion develops and the surface winds decrease as atmospheric mixing ceases.  Mixing brings drier air down to the ground - when this stops, relative humidity and heat indices increase accordingly.

Milwaukee Heat Indices  Madison Heat Indices

Southcentral and Southeast Wisconsin - Temperature Records

The tables below show observed and record high temperatures and record high mininum temperatures for July 1-7 in Milwaukee and Madison. 

Milwaukee MaxTemp Record Max Min Record High Min
Sun July 1st 84 99 in 1931 70 78 in 1910
Mon July 2nd 87 98 in 1911 69 77 in 1911
Tue July 3rd 97 99 in 1911 73
75 in 2002 & 1921
Wed July 4th 102-new record 98 in 1990 81-new record  79 in 1999
Thu July 5th 103-new record 96 in 1911 73  78 in 1921
Fri July 6th 94 99 in 1988 76 79 in 1921
Sat July 7th 86 98 in 1980 & 1936 68 75 in 1988

Madison MaxTemp Record Max Min Record High Min
Sun July 1st 95 97 in 1931 & 1910 62 77 in 1901
Mon July 2nd 97-new record 96 in 1911 70 75 in 1911 & 1872
Tue July 3rd 96-tied record 96 in 1949 & 1911 78-new record 74 in 2002 & 1897
Wed July 4th 102-new record 98 in 1955, 1949 & 1911 81-new record  77 in 1999 & 1897
Thu July 5th 104-new record 98 in 1911 75-new record  74 in 1999 & 1939
Fri July 6th 102-new record 100 in 1886 76 83 in 1874
Sat July 7th 89 102 in 1936 72 79 in 1876

Previous to this year, the last time high temperatures reached 100 degrees or higher in Milwaukee was July 14, 1995 and in Madison, July 13, 1995.

The tables below show the top ten hottest days on record in Milwaukee (records go back to 1871) and Madison (records go back to 1869). Milwaukee and Madison both had several days make the list during this heat wave.

Milwaukee
Rank Value Date
1 105 7/24/1934
2 104 6/1/1934
3 103 7/5/2012
    7/13/1995
    8/1/1988
6 102 7/4/2012
    7/14/1995
    7/25/1940
    7/30/1916
10 101 6/21/1988
    6/14/1987
Madison
Rank Value Date
1 107 7/14/1936
2 106 7/13/1936
3 104 7/5/2012
    7/10/1976
    7/12/1936
    7/21/1901
 7  102 7/4/2012
   102 7/6/2012
    8/17/1988
    8/16/1988
    7/14/1977
    7/7/1936

Madison tied for 3rd for the most consecutive days of high temperatures greater than or equal to 90 degrees (table on left) and tied for 2nd for most consecutive days of high temperatures greater than or equal to 95 degrees (table on right). Not to mention, Milwaukee and Madison both tied for the 2nd most consecutive days with high temperatures of 100 degrees or higher, with Milwaukee having two consecutive days and Madison, three.

Rank Consecutive Days End Date
1 15 7/27/1901
2 13 7/18/1936
3 10 7/6/2012
  10 9/3/1953
5 9 7/10/1989
  9 8/4/1988
Rank Consecutive Days End Date
1 8 7/14/1936
2 7 7/6/2012
  7 7/06/1936
  7 8/21/1955
  7 7/25/1901
6 6 7/25/1934
  6 7/1/1931

Central and Northeast Wisconsin - Temperature Records

Date Location Record Temp
Mon July 2nd  Marshfield Max T 94
Wed July 4th  Wausau Max T 96
   Marshfield Max T 96
   Stevens Pt Max T 97 (T)
   WI Rapids Max T 102
Thu July 5th Green Bay Max T 99
   Wausau Max T 96 (T)
   Manitowoc Max T 97
   Oshkosh Max T 100
   WI Rapids Max T 101
Fri July 6th  WI Rapids Max T 100

Westcentral Wisconsin - Temperature Records

La Crosse MaxTemp Record Max Min Record High Min
Sun July 1st 94 100 65 77
Mon July 2nd 99 103 73 77
Tue July 3rd 99 100 75 79
Wed July 4th 103-new record 100 in 1911 81-new record 80 in 1999
Thu July 5th 98 101 79-new record 77 in 1900
Fri July 6th 103-new record 100 in 1989 78- tied record 78 in 1886
Sat July 7th 86 104 in 1980 & 1936  70 77
 

Additonal details on the heat wave in the Midwest can be found on these web sites:

WFO Green Bay

WFO La Crosse

WFO Minneapolis/Chanhassen


MEB/MBK/PC/ET/JJW/JCW/REM/MG/AFK
NWS Milwaukee/Sullivan 



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