April 21, 2011 5:02 pm EarthWatch Forecast April 21: Frost Advisory No, you didn’t read that wrong, there’s a frost advisory in effect for counties surrounding Philadelphia. US & World Videos 2:43 Philly is warmer than Miami, Florida, Monday 2:06 Feeling like summer 2:36 A summer preview 2:50 One more cool day, then warmer weather ahead 3:15 Cold night, then a big warmup this weekend