November to May is the main visitor season: dry, warm, and reliable. Temperatures range from a comfortable 20°C at night in December to 30°C in May. This is also whale shark season in the Sea of Cortez (October to May), and humpback whale calving season near Cabo (January to March). Spring Break in March and April brings heavy crowds and inflated prices.
June to October is the hot, humid season with hurricane risk peaking in September. Summer temperatures regularly reach 38°C. Diving and fishing are excellent in summer — the water is warmest and dorado, marlin, and wahoo are running — and prices are substantially lower. Tropical storms affect the region roughly once every few years; most cause heavy rain rather than severe damage in San José itself, but it is worth monitoring the forecast.
The clear shoulder windows — October and early November — offer the best combination of comfortable temperatures, lower prices, and the start of the fishing and whale season.