Hi zpc, I'm in Greece right now and enjoying the cooler (!) weather than back home in Tel Aviv. I'm hoping that by the time I get home (just a couple days before you arrive) I won't have to run the AC more than 2-3 hours a day.
Expect to wear sandals all the time, except at archaeological sites where sneakers are more comfortable because of uneven ground and lots of pebbles/sand. The topography is varied, in Jerusalem you'll probably need long sleeves or a light jacket in the evenings and possibly the early mornings. Sun hat is a good idea. You'll want knees and shoulders covered for many religious sights, but you'll see most people in short sleeves and capris/shorts still. The fashion-conscious young women may be sporting stylish boots, long sleeves, long pants and even jackets, but that's in spite of, not because of , the temps. Tel Aviv, Haifa, and around the sea of Galilee are likely to be somewhat humid,, pleasantly cool in the afternoon. If Israel is lucky (and you aren't) there may be a little rain.