Unlike the rest of the Northern Hemisphere Panama has Summer (Verano) now. It's a bit confusing to foreigners and when foreigners talk about Summers it's very confusing to Panamanians.
Summer here is the "Non Rain" season. With beautiful sun shine, nice breezes and generally excellent weather. It lasts from December to April and is the traditional time here for going to the beach, country fares and carnevals.
All I can say is I love it. The last month I've hardly seen any rain fall, its still green as ever. After more than 6 months of rainy weather it's great.