At 20:00 (8:00 PM) there was a sharp rise in temperature. This temperature rise is related to an increase in wind speed. The increased wind speed was caused by a heat burst. In a heat burst, virga evaporates, cooling the air making, and becomes more dense. The air suddenly sinks and compression causes adiabatic warming. At the surface, people experience sudden gusts of warm air.
Mesowest profile of temperature and wind in Milwaukee on May 14, 2013:
National Weather Service description of the Heat Burst:
Virga and heat burst video (go to 8:00 PM)
More about heat bursts: