If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Glengarriff: The hottest months are usually July and August with an average temp of 57°F, while the coldest months are March and January with an average of 45°F. The rainiest months in Glengarriff are December, November, October, and January, with each month seeing an average of 7 inches of rainfall.