September in Richardson averages a daily high of 31.3°C with nights around 20.3°C. Expect roughly 6.1 wet days totalling 82.6mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Richardson is March–April.
Based on RICHARDSON, TX US (5.5km), 1995–2024. 19 years of September data.