In Israel, summer lasts at least half the year (April/May to October/November). In Jerusalem, temperatures by day are hot and dry, dropping substantially at night. Winter (November to April) sees cold periods and heavy rains interspersed with an occasional snowfall and spells of pleasant, spring-like weather. The transition seasons sometimes bring a hamsin, a hot, dry desert wind, which lasts up to several days.
Average daily temperatures in Jerusalem are: January 6.5-12.8 C (44-55F); August 20-29.7 C (68-85F).
You can check out Israel's weather on the Internet at: www.accuweather.com