If you plan to visit the entire country, the best months are October-December, when temperatures are relatively mild and nights are cool (88-71 F/31-22 C). Temperatures are lower in the northern part of the country, so take along a sweater or a jacket at this time. May-September is the hot, humid monsoon season in the south (92-76 F/33-24 C). January-March is foggy and drizzly in the north. The mountains can be quite cold in winter, with occasional snowfall at higher elevations.