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 Sincelejo: The hottest months are usually February and March, with an average temperature of 28°C, while the coldest months are November and December, with an average of 26°C. The rainiest months in Sincelejo are August, May, October and September, with each month seeing an average of 257 mm of rainfall.