Planning for the weather is a good way to make your trip to San Cristóbal de las Casas relaxing and enjoyable, especially when you're splurging. The hottest months are usually April and May, with an average temperature of 19°C, while the coldest months are January and December, with an average of 16°C. The rainiest months in San Cristóbal de las Casas are June, September, August and July, with each month seeing an average of 483 mm of rainfall.