San Cristóbal de las Casas weather in May

San Cristóbal's forum describes September rain as genuinely hard to predict - it can be pouring in one town and clear and sunny in the next over these mountain roads, day or night. What's more consistent is the temperature swing: pleasant, jacket-optional days in the low 20s C give way to genuinely cold nights, cool enough that posters recommended a proper warm layer for any evening walk. It's a notably different climate from the hot, humid lowlands nearby, which is part of why San Cristóbal draws visitors even in the rainy season.

Forum posters describe this high-altitude town (around 7,200ft) as running noticeably cooler than lowland Mexico even outside its coldest months - January highs typically in the mid-60sF with lows near 40F set the baseline, and March, while milder than January, still carries a real overnight chill given the elevation. Posters consistently note most hotels lack central heating, though extra blankets are commonly provided, so packing warm layers for evenings matters regardless of the season. Unlike the summer rainy season - when posters describe reliably sunny days followed by an hour or two of afternoon/evening rain - March sits in the drier part of the year, generally sunny with a lower overall rain chance.