Fresno has one of the most extreme climates of any major American city. Summers are brutal — temperatures regularly exceed 105°F (41°C) between June and September, with little humidity but also little relief. If you must come in summer, plan outdoor activities for early morning and late afternoon; midday is genuinely uncomfortable even for acclimatised locals.
The best times to visit are spring (March–May) and autumn (September–November). Spring coincides with the Blossom Trail (late February to March), the best wildflower displays in the Sierra Nevada, and optimal conditions for Yosemite — high waterfalls, open roads, moderate crowds. Autumn brings mild temperatures, harvest season produce at roadside stands, and clear skies.
Winter is mild by most standards (lows rarely below freezing in the valley) and offers ski season in the Sierra Nevada. The valley experiences frequent tule fog from November through February — a dense, ground-level fog that can reduce visibility to near zero for days and makes driving hazardous. Airport delays during fog season are common.