You can visit Myanmar all the year round but the best time to come is between October and February.
Myanmar has three seasons:
Cool Season – October through February, with average temperatures of 20-24 C
Hot Season – March through May, with average temperatures of 30-35 C
Wet Season – June through September, with average temperatures of 25-30 C.
The ideal time to visit Myanmar is during the cool season.
However, even during the wet season, while Yangon normally receives morning and afternoon showers, rainfall in Bagan and Mandalay is very low. The weather around Inle Lake and in Shan State is quite pleasant all year round, but cold at night from December to February.