The North of Mexico has the mildest climate. You can pretty much go any time of year, although it does rain a lot from July to September. If you feel the cold easily, avoid February and March, when temperatures are at their lowest, albeit rarely below 5°C/41°F. It's here, in the North, that you'll find some amazing, sunny, colourful, colonial towns, not forgetting Chihuahua, the country's biggest state, as well as the buzzing city of Monterrey. History fans and desert lovers will adore the North of Mexico.
March and April as well as October and November are best for touring central Mexico and Mexico City. You'll avoid the rains and you won't feel too hot whilst touring the country's cosmopolitan capital. It's a charming place, full of lively markets and streets, with plenty of parks in which to relax. And it goes without saying that it's a great departure point for visiting local, archaeological sites; the temples at Teotihuacan are a must!
Between mountains and deserts, sits the huge plain of El Bajio. Stopover at Querétaro to see its old quarter, complete with colonial architecture and baroque fountains. There's also Guanajuato and its blend of impressive civic and religious architecture. Its houses are brightly coloured and its people cheery. Sitting at 1,500m high, you can go during the dry season, including May, without suffering from the heat. At the same time, avoid the rainy season from June to October.
To not go diving in Mexico is almost unforgiveable. The Caribbean coast is home to the second largest live barrier reef in the world. Rub up close to colourful, tropical fish as well as dolphins, whales and sea turtles. Dive in the warm, clear seas of Banco Chinchorro or Isla Mujeres and weave your way around the coral banks of Bahias de Huatulco. If diving is your passion then you musn't miss the island of Cozumel, one of the best dive spots in the world. Best to go between February and June.