April–June is the best time. Temperatures are pleasant (18–26°C), the garrigue is fragrant with rosemary and thyme in flower, and the Saturday market is running in full spring form. Late May and early June bring the lavender into early bloom in the fields to the north and east of town — not yet at peak, but the colour is already dramatic.
July is busy and warm (often 30°C or above), and the town fills with French summer visitors. The Saturday market is at its most lively, and Uzès hosts several festivals, including music and theatre events under the Duché walls. It is worth experiencing once, but expect the Place aux Herbes to be packed by mid-morning.
August is best avoided if you dislike crowds and heat. The town is at its busiest and hottest, parking in the surrounding countryside becomes a project, and prices at restaurants and accommodation climb accordingly. If you must go in August, arrive before 9am on market day and plan a long midday retreat indoors.
September–October are nearly as good as spring. The summer visitors have gone, the light turns golden, and the garrigue takes on a dry, aromatic warmth. Harvest season means local markets have walnuts, wild mushrooms, and the new season's olives. This is when the town feels most like itself.
November–March is quiet and cool. Some restaurants and shops reduce hours, and the weekend market is smaller, but the Duché and cathedral are still open and essentially crowd-free. Not an obvious winter destination, but cheap and peaceful.