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 Shillong: The hottest months are usually June and August, with an average temperature of 21°C, while the coldest months are January and December, with an average of 14°C. The rainiest months in Shillong are July, June, August and September, with each month seeing an average of 903 mm of rainfall.