Winter is the prime season: October through April brings warm, sunny days (70–85°F), comfortable evenings, and the full range of cultural events. The Coachella and Stagecoach music festivals in April draw enormous crowds to nearby Indio — accommodation books up months ahead and prices surge. Modernism Week in February is the peak of architectural tourism.
Summer is brutal. July and August regularly see temperatures above 110°F, and even at night it stays warm. Most visitors avoid the city entirely; those who come benefit from dramatically lower hotel prices and empty restaurants. If you do visit in summer, plan outdoor activities for before 8am or after sunset.
The brief wildflower season (February to March in a good rain year) can transform the surrounding desert into a carpet of colour. Check the Desert Sun for bloom reports — it varies widely by year.