The best time to visit Mexico is during the dry season, from November to April. Between June and October the rains are frequent, short-lived and won't stop you from enjoying most regions. May is dry but really hot - not the best time of year to visit. You'll find that the climate varies according to altitude. Winters are cold and days short in mountainous regions, whilst the southern lowlands are hot all year round. Overall, if you're planning a trip to this Mayan homeland, choose the dry, pleasantly warm periods.