Mulegé: when to go? Whether you love the heat or the cold, if you're planning a trip here, it could be useful for you to know: June, has temperatures that can reach 33°C, it's the hottest month at this touristic destination. January instead is the coldest month, where temperatures can trop to 21°C. The water temperature of the sea can go from 30°C in the summer months to 18°C during the coldest months.