Mexico is blessed with a mostly moderate climate that makes for pleasant traveling year round. Peak tourist season varies with location but mid November to early May are the months that you may need to make your reservations well in advance for. The desert areas, especially in mid and southern Baja can get very hot in summer and the mountainous regions tend to be on the cold side the winter. Most of the beaches to the south of the Tropic of Cancer tend to be pretty humid in the summer and are prone to afternoon rains. Afternoon and evening rains are a fairly common occurrence during the summer in much of Mexico, including the Guadalajara and Mexico City areas. Check our Weather page and our Average Temperature Page for some insight as to what the local weather conditions may be at any given time of year.
Mexico is in general warmer than the US, but don't assume! Mexico City, for example, is at a high altitude and thus very temperate while Cancun is a tropical paradise. Before you go, check the usual conditions at your destination.
However, serious occurrences of either are infrequent, and in fact there are active volcanoes that can be visited by intrepid tourists!
On the coast, especially along the Baja and Pacific coast, the sea breeze is usually strong and helps keep sunbathers and vacationers blissfully cool despite the bright sunshine.
The best advice, just as when traveling anywhere, is to call ahead and see what the climate is like at your destination … pack and plan to dress accordingly!