1995 Chicago Heat Wave - Weather

Weather

The temperatures soared to record highs in July with the hottest weather occurring from July 12 to July 16. The high of 106 °F (41 °C) on July 13 was the second warmest July temperature (warmest being 110 °F (43 °C) set on July 23, 1934) since records began at Chicago Midway International Airport in 1928. Nighttime low temperatures were unusually high; in the upper 70s and lower 80s °F (about 26 °C)—as well. Record humidity levels also accompanied the hot weather. The heat index reached 119 °F (48 °C) at O'Hare airport, and 125 °F (52 °C) at Midway Airport.

At the peak of the heat wave, as was the case in the summer of 1988, and possibly 1977, Madison, Wisconsin probably would have broken its all-time maximum temperature record of 107 °F (42 °C) had the reporting station been in the same location as it was during the 1930s.

The humidity made a large difference for the heat in this heat wave when compared to the majority of those of the 1930s, 1988, 1976–78 and 1954–56, which were powered by extremely hot, dry, bare soil and/or air masses which had originated in the desert South-West. Each of the above mentioned years' summers did indubitably have high-humidity heat waves as well, although 1988 was a possible exception in some areas. Moisture from previous rains and transpiration by plants drove up the humidity to record levels and the most humid air mass originated over Iowa previous to and during the early stages of the heat wave. Numerous stations in Iowa, Wisconsin, Illinois and elsewhere reported record dew point temperatures above 80 °F (27 °C) with a probable peak at 86 °F (30 °C) reported from at least one station in Wisconsin on 13 July 1995; this added to the heat to cause heat indices above 130 °F (54 °C) in Iowa and southern Wisconsin on several days of the heat wave as the sun bore down from a cloudless sky and evaporated even more water seven days in a row.

A more typical result of surface dew points above 80 °F (27 °C) are extreme precipitable water readings as well as other indices used to forecast severe thunderstorms and flooding such as Convective available potential energy as was illustrated in early June 2008 when thunderstorms originating in Minnesota and Iowa mushroomed when hitting the area of extreme dew points in South-Central and South-East Wisconsin from 77 to 84 °F (25 to 29 °C) and inaugurated the third wave of upper Middle West flooding (the first was snowmelt from the record-breaking winter snows and the third was the widespread rains in excess of 10 inches (254.00 millimetres) and up to 21 inches (533.40 millimetres) during early August 1997) by producing extremely heavy rain over the region, with many areas receiving 5 inches (127.00 millimetres) and a few areas of 10 to 15 inches (250 to 380 millimetres) in 3 to 6 hours' time.

A few days after, the heat moved to the east, with temperatures in Pittsburgh, Pennsylvania reaching 100 °F (38 °C) and in Danbury, Connecticut, 106 °F (41 °C) which is Connecticut's highest recorded temperature.

Dew point records are not as widely kept as those of temperature, however the dew points during the heat wave were at or near national and continental records. The world record most likely being close to or in excess of 100 °F (38 °C) at locations along the Red Sea coast of Saudi Arabia.