Yesterday we topped out at a very muggy 89°. The dewpoint hovered around 80 at one point indicating extremely muggy conditions. Later in the afternoon towering cumulus clouds developed and then two lines of fast moving storms moved through between 6 and 8 PM. Mammatus clouds appeared overhead prior to the arrival of the thunderstorms. Rainfall amounted to 0.59 inch and we experienced a peak gust of 35 mph. Higher gusts were measured between Coal City and Mazon and areas from Rockford to Chicago had torrential rains yesterday of between 3 and 4 inches.