May in Reston averages a daily high of 22.3°C with nights around 11.6°C. Expect roughly 13.4 wet days totalling 114.7mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Reston is August–October.
Based on VIENNA, VA US (9.6km), 1995–2024. 29 years of May data.