South of the tropic of Cancer (which cuts across Mexico north of Tampico) it's hot and humid, particularly along the coastal plains and the Yucatan peninsula. Inland, at higher elevations, it's much drier and temperate. Mountain areas can get very cold in winter, and often have snow.

The hot, wet season is from May to October. Rain ranges from late afternoon downpours to days of prolonged rain. The Yucatan peninsula is the area most affected in the hurricane season - June to October.

Average Daytime temperatures:
Yucatan 27C (81F) in January and 32C (90F) in July
Mexico City 19C (66F) in January and 23C (73F) in July
San Cristobal 20C (68F) in January and 22C (72F) in July
Oaxaca 25C (77F) in January and 27C (82F) in July.