The recent shift from hot weather to cold weather in the Northeast is causing concern for flower and fruit farmers who fear they may lose some crops due to the sudden drop in temperature. The average date of the last frost usually ranges from mid-April to early June, but the unusually warm weather in April could cause problems. The National Weather Service has issued a freeze warning for parts of Ohio, Pennsylvania, Virginia, Maryland, and North Carolina. The weather has also affected operations at Understory Farm in Vermont, where tulips that were supposed to be ready for Mother’s Day in mid-May have already bloomed.