If you're hoping to get lost in the rain on your romantic getaway, take a look at these details about year-round temperatures in Butwal: The hottest months are usually May and April, with an average temperature of 31°C, while the coldest months are January and December, with an average of 19°C. The rainiest months in Butwal are July, August, June and September, with each month seeing an average of 372 mm of rainfall.