Many travellers have described San Marcos as having the perfect climate, it is not too humid, the sun is always out and there are not too many mosquitos.
San Marcos has two main seasons –the dry season (from November to April) and the wet season (from May till October). The dry season is the main season when most tourists are visiting.
During the wet season mornings are usually sunny but you can expect rain in the afternoon for 2 hours or so. The perfect opportunity to spend a few hours in the afternoon in one of the cozy cafés here in San Marcos.
In November the winds arrive at the lake so it can be a bit cooler in the evenings.
The elevation of San Marcos is 1570 m (5 150 ft.) so expect it can be colder in the evenings and at night but plenty of sunshine in the day and high temperatures.
In general – you can wear summer clothes all year round and have something warm for the evenings. Please bare in mind that this is still a very traditional town and dress appropriately.