The best time to visit Fontana, California, is generally during the spring and autumn months, specifically from April to May and September to October.During these periods, the weather is pleasantly warm without the intense heat of summer, making it ideal for outdoor activities and exploring the region. You'll find average temperatures ranging from the low 20s to high 20s Celsius, with plenty of sunshine and minimal rainfall. This allows for comfortable visits to attractions like the Auto Club Speedway or day trips to nearby natural parks.For those looking to avoid crowds and potentially find better value on accommodation, visiting in late spring or early autumn can be particularly advantageous. The summer months (June-August) can be very hot, with temperatures often exceeding 35°C, which might be less comfortable for extended outdoor exploration.