(Portland, OR) -- Hot weather and summer travel have resulted in a shortage of blood donations. The American Red Cross says that since July 1st, the national blood supply has dropped 25 percent and demand from hospitals remains strong. The hot weather in July across many states, along with summer vacations, reduced the number of donors at more than 100 blood drives in nearly every state. The Red Cross is trying to increase donations of blood, platelets, or plasma this month by offering a 20-dollar Amazon gift card by email. You can preregister and make a donation appointment at Red Cross Blood dot org.