BT Yom 29a(2) :שילהי קיטא קשו מקיטא‏ : the last days of summer are harder (to bear) than the summer (itself)
See the entire entry for qəšē adj. hard

BT Yom 29a(2) :שילהי קיטא קשו מקיטא‏ : the end of summer is more severe [i.e. hotter] than summer
See the entire entry for ša/ilhē n.m.cs. end, dissolution