If you’re looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Siaya: The hottest months are usually February and March, with an average temperature of 24°C, while the coldest months are June and July, with an average of 22°C. The rainiest months in Siaya are April, May, November and October, with each month seeing an average of 306 mm of rainfall.