"As yet exaltest thou thyself against my people, that thou wilt not let them go? Behold, to morrow about this time I will cause it to rain a very grievous hail, such as hath not been in Egypt since the foundation thereof even until now." - the Bible

If this is summer, make it stop...excessively high humidity...monsoon-like rainstorms with accompanying crashes of thunder and lightening...and talk of hail later in the day...