Cajamarca has a pleasant highland climate: cool nights year-round (temperatures drop below 10°C most nights), mild days (15–20°C), and clear air. The main distinction is between the dry season (May to October) and the wet season (November to April). The dry months are the most comfortable for walking and sightseeing; the wet season brings afternoon showers but also turns the surrounding hills a vivid green.
The most important local event is Carnaval, celebrated in Cajamarca with an intensity that makes it one of the most famous in Peru — considered by many to be the best Carnaval celebration in the country after Rio de Janeiro. It falls in February or March (depending on Easter) and involves several days of street processions, dancing, water fights, and general exuberance. Book accommodation well in advance if you plan to come for Carnaval.