Bucaramanga's altitude — around 960 metres — keeps temperatures stable throughout the year, hovering between 18°C and 28°C with little variation between seasons. There is no bad time to visit in a strict meteorological sense, but there are drier and wetter periods worth knowing about.
The two dry seasons run from December to February and from June to August. These are the most comfortable months for hiking in the Chicamocha canyon and for day trips to San Gil, where the rivers run lower and white-water conditions are safer to assess before committing. The dry season also makes Girón particularly pleasant — the colonial streets aren't being rained on and afternoon light in the whitewashed lanes is excellent.
Rain falls most heavily in April, May, October, and November. The city itself handles it without drama — showers tend to come in the afternoon and last an hour or two before clearing — but the canyon road can get muddy and the river activity at San Gil operates on a smaller number of days. If you're coming primarily for adventure sports, the June–August window is the most reliable.
Semana Santa (Easter week) brings Colombians from Bogotá and the coastal cities to Bucaramanga. Hotels fill up and Girón in particular gets crowded, though the atmosphere is festive. Bucaramanga's own Feria Bonita, held in late June or early July, centres on Parque Santander with concerts, food stalls, and the usual crowded streets. It's worth overlapping with if you happen to be in the region.