Sea of Cortez in September

October through April offers the sweet spot – warm days, cool nights, and calm seas perfect for diving and snorkeling. Water temperatures stay around 75-80°F, which means you can swim comfortably without a wetsuit. This is also whale season, when gray whales migrate south to breed in the lagoons. Humpbacks and blue whales show up too, making it one of the world's best whale watching destinations. December through February brings the coolest air temperatures, sometimes dropping to the 50s at night, but days still hit the 70s. March and April heat up but stay pleasant, with fewer crowds than winter months. May through September gets brutally hot – we're talking 100°F+ in the shade – but this is when you'll find the best deals and have beaches to yourself. Hurricane season runs June through November, though direct hits are rare. The water's warmest in late summer, hitting 85°F, which brings out tropical fish species you won't see in cooler months. Just pack plenty of sunscreen and plan indoor activities for midday.