There’s not really a bad time, weather-wise, to visit Tel Aviv. Its prime position on the Mediterranean Sea makes for hot and humid summers and cool-but-not-unpleasant winters (temps sometimes dip down to the 40s, and the last time it snowed was 1950). Even during the hottest months (July, August, and September), breezes start to stir in the evenings. This same period brings almost no rain, either—January is usually the wettest.
Religious holidays are observed here (during Yom Kippur, almost every business is closed), but the adherence is more lighthearted than austere; you’ll find plenty of people riding bikes to the beach rather than hunkering down in synagogues. When in doubt, remember the oft-repeated mantra Jerusalem prays, Tel Aviv plays.
As in most other big cities, summer brings a laundry list of cultural festivals: outdoor concerts in parks like Ganai Yehoshua, weekslong dance series at the Suzanne Dellal Center in the bourgeois-bohemian neighborhood of Neve Tzedek, and theater with the Habmiah and Cameri companies. Want parades? Gay Pride (June) is a huge one, and it epitomizes the open-mindedness of the city. Purim (March), the most fun holiday on the Jewish calendar, goes off here more than anywhere else in Israel (and possibly the world).