| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 4.2° | -3.8° | 87.4mm | 10.2 | 20 |
| February | 6.3° | -2.7° | 74.3mm | 9.8 | 30 |
| March | 11.5° | 1° | 91.4mm | 9.8 | 52 |
| April | 17.9° | 6.3° | 89.5mm | 11.1 | 71 |
| May | 22.6° | 11.5° | 111.3mm | 11.8 | 76 |
| June | 26.7° | 16.1° | 119.2mm | 10.9 | 78 |
| July | 29.1° | 18.5° | 113.3mm | 10.1 | 71 |
| August | 28.2° | 17.9° | 107.1mm | 9.6 | 76 |
| September | 24.3° | 14.3° | 126.2mm | 9.2 | 82 |
| October | 18.2° | 8.3° | 101.9mm | 8.9 | 76 |
| November | 11.8° | 2.6° | 81.7mm | 8.3 | 57 |
| December | 6.6° | -1.2° | 97.3mm | 10 | 32 |
January in Gaithersburg averages a daily high of 4.2°C with nights around -3.8°C. Expect roughly 10.2 wet days totalling 87.4mm. A hard month to visit for comfort alone.
February in Gaithersburg averages a daily high of 6.3°C with nights around -2.7°C. Expect roughly 9.8 wet days totalling 74.3mm. A hard month to visit for comfort alone.
March in Gaithersburg averages a daily high of 11.5°C with nights around 1°C. Expect roughly 9.8 wet days totalling 91.4mm. Demanding conditions — pack for it and plan indoor options.
April in Gaithersburg averages a daily high of 17.9°C with nights around 6.3°C. Expect roughly 11.1 wet days totalling 89.5mm. Generally workable, with some weather to plan around.
May in Gaithersburg averages a daily high of 22.6°C with nights around 11.5°C. Expect roughly 11.8 wet days totalling 111.3mm. Comfortable conditions for being outdoors all day.
June in Gaithersburg averages a daily high of 26.7°C with nights around 16.1°C. Expect roughly 10.9 wet days totalling 119.2mm. Comfortable conditions for being outdoors all day.
July in Gaithersburg averages a daily high of 29.1°C with nights around 18.5°C. Expect roughly 10.1 wet days totalling 113.3mm. Generally workable, with some weather to plan around.
August in Gaithersburg averages a daily high of 28.2°C with nights around 17.9°C. Expect roughly 9.6 wet days totalling 107.1mm. Comfortable conditions for being outdoors all day.
September in Gaithersburg averages a daily high of 24.3°C with nights around 14.3°C. Expect roughly 9.2 wet days totalling 126.2mm. Comfortable conditions for being outdoors all day.
October in Gaithersburg averages a daily high of 18.2°C with nights around 8.3°C. Expect roughly 8.9 wet days totalling 101.9mm. Comfortable conditions for being outdoors all day.
November in Gaithersburg averages a daily high of 11.8°C with nights around 2.6°C. Expect roughly 8.3 wet days totalling 81.7mm. Generally workable, with some weather to plan around.
December in Gaithersburg averages a daily high of 6.6°C with nights around -1.2°C. Expect roughly 10 wet days totalling 97.3mm. A hard month to visit for comfort alone.
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. Gaithersburg peaks at 82.
Based on 30 years of records, August–October scores highest for comfort in Gaithersburg, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 29.1°C.
September is the wettest, averaging 126.2mm of rain across roughly 9.2 wet days.
January is the coolest month, with average daily highs around 4.2°C.