The temperature in New York climbed into the 80s for three days last week. Air conditioners went on all over the city, and out came the flip-flops, T-shirts and shorts. But it’s still April, the fake-out month of the year here. Today (Saturday), the high will be 65, then 56 on Sunday and 51 on Monday, with nights in the 40s. Spring remains fickle. [Phot…