Toluca's altitude makes it the coldest of Mexico's state capitals — temperatures rarely climb above the low twenties Celsius and nights can drop close to freezing in December and January. Pack a sweater whenever you visit.
November to April is the dry season, the best window for getting up the Nevado de Toluca volcano (where the access road is more often open) and for clear views of the surrounding mountains. May to October brings afternoon thunderstorms; mornings are generally clear, evenings often wet.
The two great festivals are the Feria del Alfeñique (the sugar-skull fair, in the second half of October running into the Day of the Dead) and the Las Mañanitas celebrations for the patron saint in early November — both fill the Portales with vendors and music for several days.