September in Lewisville averages a daily high of 32.2°C with nights around 19.3°C. Expect roughly 6.5 wet days totalling 77.5mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Lewisville is March–April.
Based on GRAPEVINE DAM, TX US (12.1km), 1995–2024. 22 years of September data.