Weather is probably a major factor when you plan your trip to South West Bay, and keep in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually March and February with an average temp of 79°F, while the coldest months are August and July with an average of 76°F. The rainiest months in South West Bay are March, January, February, and April, with each month seeing an average of 15 inches of rainfall.