Madison finally broke the 90 degree mark Tuesday. The official high was 92 degrees. Milwaukee came within 1 degree late this morning before the lake breeze pushed through.
For the meteorological summer months of June, July and August, both Milwaukee and Madison failed to reach 90 degrees or warmer. Both cities however, have come close on a number of days.
Milwaukee's warmest temperature during the year has been 89 degrees, which was reached Tuesday. However for meteorological summer, Milwaukee's highest temperature was 88 degrees on July 15th, 16th, 30th, and August 5th.
The last time Milwaukee did not reach 90 degrees or warmer during the summer months was in 2000, and in the previous summers of 1915, 1882 and 1877.
The average number of days with 90 degrees or warmer each year in Milwaukee is nine, which is based on the 30 year average from 1971 to 2000.
Madison's warmest temperature for the year has been 92 degrees, which occurred Tuesday. The warmest temperature for meteorological summer was 88 degrees, which was reached on July 16th and most recently on August 31st.
The last time Madison did not reach 90 degrees or warmer during the summer months was in 2004, and in the previous summers of 1924, 1915, 1907, 1906, 1903, 1902, 1884, 1883, 1882, 1877, 1875, and 1869
The average number of days with 90 degrees or warmer each year in Madison is 12, based on the 30 year average from 1971 to 2000.
Several possible reasons why temperatures did not get warmer this summer in southern Wisconsin include:
One possible reason is due to the heavy rainfall of June. With this excessive rainfall came nearly saturated sub soils. When the air temperature increases into the 80s with sunny conditions...deep soil moisture evaporates more easily. Evaporation is a cooling process...thereby making it more difficult for surface temperatures to rise much higher than the upper 80s.
Another reason we haven/t reached 90 yet is when a warm airmass tries to nudge toward southern Wisconsin...clouds and scattered thunderstorms have developed along the tight temperature gradient known as a baroclinic zone...sending rain cooled air into southern Wisconsin. This has happened numerous times over the summer as weak cold front followed each brief influx of warm air.
Also, the upper level steering winds for much of July and August have been from the west or northwest across the upper midwest, which have contributed to keeping the hot and more humid air to the south of Wisconsin.
Of course, one can't rule out the cooling influence of the cooler waters of Lake Michigan. When surface winds come out of the northeast, east, or southeast. they are cooled by the water. In order to get up to 90 degrees or higher in Madison and Milwaukee we need southwest to west winds pulling warm to hot air in from the Great Plains. This hasn't happened with any persistence or regularity over southern Wisconsin during the 2008 summer season.
A warm and humid southerly air flow ahead of an approaching cold front will result in the best chance for Madison and Milwaukee to reach 90 degrees on Tuesday, September 2nd. Cooler air will then settle over southern Wisconsin for the remainder of the week.
Below is an image showing the number of days with 90 degrees or higher at Milwaukee (MKE) within each decade, as well as the same kind of information for 95 or higher and 100 or higher. Keep in mind that the 2000's have not finshed - we still have the remainder of 2008, and then 2009 to take into account. However, notice the larger number of days with 90 degrees or higher back in the 1930s, 1940s, and 1950s with a gradual downward trend since the 1980s.
Below is an image showing the number of days with 90 degrees or higher at Madison (MSN) within each decade, as well as the same kind of information for 95 or higher and 100 or higher. Keep in mind that the 2000's have not finished - we still have the remainder of 2008, and then 2009 to take into account. However, notice the larger number of days with 90 degrees or higher back in the 1930s, 1940s, and 1950s with a gradual downward trend since the 1970s.
Below is a chart showing the number of days with maximum temperatures of 90 or higher by month for both Milwaukee and Madison, for the period of 1871 through July 2008:
Below is a line graph showing the number of days 90 degree or higher for both Milwaukee and Madison, by the year, for the period of 1871 through 2006. Milwaukee had 36 days with 90 degrees or higher in 1988 and 33 days in 1955. Madison had 40 days with 90 degrees or higher in 1955 and 35 in 1988.
Research and graphs generated by Student Volunteers: Melissa Peterson (2008) and Stephanie Ludwig (2007).