The dry season — January to March and June to October — is the best time for the climb: clear views, dry trails, and no risk of being caught on a steep slope in a thunderstorm. Wet season afternoons can bring heavy rain that turns the trail into a mudslide.
Whatever the season, set off as early as possible. The trail has no shade, the lava rock holds heat, and the rim views are clearest before mid-morning. Aim to be off the rim by noon.