| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 5.8° | -3.8° | 82mm | 11.7 | 22 |
| February | 7.8° | -2.9° | 68.9mm | 10.1 | 33 |
| March | 12.2° | 0.6° | 83.3mm | 10 | 53 |
| April | 18.6° | 6° | 80.7mm | 10.4 | 75 |
| May | 22.3° | 11.6° | 114.7mm | 13.4 | 73 |
| June | 26.8° | 16.5° | 108.8mm | 11.2 | 78 |
| July | 29.1° | 19.3° | 104.1mm | 9.9 | 72 |
| August | 28.3° | 18.6° | 89.7mm | 9.8 | 75 |
| September | 24.7° | 14.7° | 102.4mm | 9 | 82 |
| October | 18.8° | 8.3° | 84.6mm | 8.9 | 78 |
| November | 13.3° | 2.2° | 68.2mm | 8.1 | 62 |
| December | 7.9° | -1.5° | 84.7mm | 10.2 | 36 |
January in Reston averages a daily high of 5.8°C with nights around -3.8°C. Expect roughly 11.7 wet days totalling 82mm. A hard month to visit for comfort alone.
February in Reston averages a daily high of 7.8°C with nights around -2.9°C. Expect roughly 10.1 wet days totalling 68.9mm. A hard month to visit for comfort alone.
March in Reston averages a daily high of 12.2°C with nights around 0.6°C. Expect roughly 10 wet days totalling 83.3mm. Demanding conditions — pack for it and plan indoor options.
April in Reston averages a daily high of 18.6°C with nights around 6°C. Expect roughly 10.4 wet days totalling 80.7mm. Comfortable conditions for being outdoors all day.
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.
June in Reston averages a daily high of 26.8°C with nights around 16.5°C. Expect roughly 11.2 wet days totalling 108.8mm. Comfortable conditions for being outdoors all day.
July in Reston averages a daily high of 29.1°C with nights around 19.3°C. Expect roughly 9.9 wet days totalling 104.1mm. Generally workable, with some weather to plan around.
August in Reston averages a daily high of 28.3°C with nights around 18.6°C. Expect roughly 9.8 wet days totalling 89.7mm. Comfortable conditions for being outdoors all day.
September in Reston averages a daily high of 24.7°C with nights around 14.7°C. Expect roughly 9 wet days totalling 102.4mm. Comfortable conditions for being outdoors all day.
October in Reston averages a daily high of 18.8°C with nights around 8.3°C. Expect roughly 8.9 wet days totalling 84.6mm. Comfortable conditions for being outdoors all day.
November in Reston averages a daily high of 13.3°C with nights around 2.2°C. Expect roughly 8.1 wet days totalling 68.2mm. Generally workable, with some weather to plan around.
December in Reston averages a daily high of 7.9°C with nights around -1.5°C. Expect roughly 10.2 wet days totalling 84.7mm. Demanding conditions — pack for it and plan indoor options.
Each month scores out of 100. It starts at 100 and loses points for daytime highs outside a 20–27°C band, for wet days, and for nights below 2°C. Nothing else is weighted in — no crowd data, no prices, no opinion. Reston peaks at 82.
Based on 30 years of records, August–October scores highest for comfort in Reston, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 29.1°C.
May is the wettest, averaging 114.7mm of rain across roughly 13.4 wet days.
January is the coolest month, with average daily highs around 5.8°C.