There's nothing like an all-inclusive holiday in Monrovia to refresh you, especially when you know what to expect from the elements. Here's some information to help you choose when to book: The hottest months are usually January and April, with an average temperature of 27°C, while the coldest months are August and September, with an average of 25°C. January and December are the driest months, while September and June are the rainiest months.