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 Cairns: The hottest months are usually January and February, with an average temperature of 27°C, while the coldest months are August and July, with an average of 21°C. The rainiest months in Cairns are January, February, March and December, with each month seeing an average of 281 mm of rainfall.