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 Sao Thome das Letras: The hottest months are usually September and October, with an average temperature of 20°C, while the coldest months are July and June, with an average of 16°C. The rainiest months in Sao Thome das Letras are December, January, November and February, with each month seeing an average of 215 mm of rainfall.