Sharav (=שָׁרָב) is the Hebrew word for heat wave and is one of the more depressing words in Hebrew. It is among the words you never want to hear, especialy not in April (but as it is, in Israel you may have a Sharav in March and in November too).
Even more depressing than “Shrav” is “Sharav Kaved” – “severe heat wave”, which basically means that anything other than staying in with the strongest AC possible is equivalent to suicide. However, there was one time when everyone in Israel was longing to hear the words “Sharav Kaved”: it was in early 1991, during the first Gulf War, when this expression was used as a code word, broadcasted on the radio, to indicate that the Iraqi Squd Missile attack was over (at least until it resumed for the next time).
I often wondered who was the genius who picked out Sharav Kaved to declare a positive status, rather than, let’s say “Mashav Ru’ach" (= Light Breeze).