October to March is the best time to visit Sambalpur. Temperatures are comfortable — daytime highs in the low to mid 20s Celsius — and the air is dry. The Hirakud reservoir fills during the monsoon and is at its most impressive in the autumn months when the water level is high and migratory birds begin arriving.
Avoid April to June if at all possible. Sambalpur sits in one of the hottest corridors of India during the pre-monsoon months: temperatures regularly exceed 45°C and the humidity makes it genuinely unpleasant. The monsoon (July to September) brings relief from the heat but roads can flood, and the jungle day trips become difficult.
The Nuakhai festival, celebrated on the fifth day after the Ganesh Chaturthi new moon (usually August or September), is the most important harvest festival of western Odisha. If you can time your visit to coincide with it, the city is alive with music, the Sambalpuri dance form of Dalkhai, and communal feasting — but accommodation will be tight.