Temperatures are expected to climb into the low 90s on Tuesday (July 18), when the mourning period known as the Three Weeks begin with the Fast of the 17th of Tammuz (Shivah Asar b’Tammuz). The “real feel” temperature may be as much as 10 degrees higher.
Readers who are fasting are urged to take extra precautions. The elderly and mildly infirm especially should stay indoors as much as possible, preferably in an air-conditioned environment. People who are seriously ill must refrain from fasting, but check with your rabbi first.
If the heat is getting to you, apply a cold, wet handkerchief to the back of your neck and sit down until you begin to cool off. If you begin to feel ill because of the heat, drink a glass of cold water immediately. If that refreshes you, return to your fast. If a few moments have elapsed and you have not improved, break your fast completely.