October to March is the time to be in Jodhpur. The temperatures settle into the comfortable twenties, the skies clear, and the evenings are cool enough to sit outside. This is when the fort visits and the bazaar wandering are most enjoyable, and when the city is most fully itself. It is also peak season, so expect higher prices and more company at Mehrangarh.
April and May are brutal. Temperatures regularly hit 45°C and the fort's sandstone radiates the heat back at you. The June and July dust storms (andhi) arrive before the monsoon, filling the air with fine desert sand. The monsoon itself lands in July and runs through September — not ideal for sightseeing, but the Thar desert responds dramatically, turning briefly green, and hotel prices drop sharply. Two festivals are worth timing a visit around: Diwali in October or November, when the old city is lit with oil lamps and the atmosphere is genuine rather than staged, and Holi in March, when the streets of Navchokiya turn into a spectacle of colour. The Rajasthan International Folk Festival (RIFF), held at Mehrangarh in October, brings folk musicians from across Rajasthan and deserves its reputation as one of the better music festivals in India.