For Annapurna Region Trekking is suited in Low altitude to high land So here are different types of weather , in this region most rainy area Lumle and rainshadow area Mustang (2535m to 4000m) and Highest peak Annapurna I ( 8091m) is suited in this region . So the weather and Climate is really different in this region.
For the trekking view most of the low land Trekking are open almost year and Highland trekking are not suggested during the winter season because of the cold , click this link:
Best time for Annapurna Region Trekking
Here I like to Describe Weather and climate by chart it is really useful for Your trips