If you are only staying the summer, dont bother taking a coat. It generally only rains and gets cold from half way through Cheshvan until Purim time.
Also, dont take seforim – not because you wont use em, but because they are cheaper there and its not worth paying extra to buy them in Chutz laaretz only to have to pay extra for baggage – and they are heavy to shlep.
P.s Dont forget teffilin.