| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 7° | -3.1° | 79.7mm | 9.7 | 31 |
| February | 8.8° | -2.2° | 79.4mm | 8.9 | 40 |
| March | 13.7° | 1.4° | 95.6mm | 10.5 | 58 |
| April | 20.4° | 6.7° | 87mm | 10.6 | 79 |
| May | 24.8° | 12.3° | 115.3mm | 11.6 | 77 |
| June | 29.4° | 17.6° | 108.7mm | 9.9 | 71 |
| July | 32° | 20.2° | 126.9mm | 9.8 | 60 |
| August | 31° | 19.6° | 114.2mm | 9.5 | 65 |
| September | 27.1° | 15.7° | 117.1mm | 9.3 | 81 |
| October | 20.7° | 8.8° | 110.7mm | 9.4 | 81 |
| November | 14.2° | 2.8° | 81.1mm | 9 | 63 |
| December | 9.1° | -1.1° | 97mm | 10.3 | 40 |
January in Rockville averages a daily high of 7°C with nights around -3.1°C. Expect roughly 9.7 wet days totalling 79.7mm. A hard month to visit for comfort alone.
February in Rockville averages a daily high of 8.8°C with nights around -2.2°C. Expect roughly 8.9 wet days totalling 79.4mm. Demanding conditions — pack for it and plan indoor options.
March in Rockville averages a daily high of 13.7°C with nights around 1.4°C. Expect roughly 10.5 wet days totalling 95.6mm. Generally workable, with some weather to plan around.
April in Rockville averages a daily high of 20.4°C with nights around 6.7°C. Expect roughly 10.6 wet days totalling 87mm. Comfortable conditions for being outdoors all day.
May in Rockville averages a daily high of 24.8°C with nights around 12.3°C. Expect roughly 11.6 wet days totalling 115.3mm. Comfortable conditions for being outdoors all day.
June in Rockville averages a daily high of 29.4°C with nights around 17.6°C. Expect roughly 9.9 wet days totalling 108.7mm. Generally workable, with some weather to plan around.
July in Rockville averages a daily high of 32°C with nights around 20.2°C. Expect roughly 9.8 wet days totalling 126.9mm. Generally workable, with some weather to plan around.
August in Rockville averages a daily high of 31°C with nights around 19.6°C. Expect roughly 9.5 wet days totalling 114.2mm. Generally workable, with some weather to plan around.
September in Rockville averages a daily high of 27.1°C with nights around 15.7°C. Expect roughly 9.3 wet days totalling 117.1mm. Comfortable conditions for being outdoors all day.
October in Rockville averages a daily high of 20.7°C with nights around 8.8°C. Expect roughly 9.4 wet days totalling 110.7mm. Comfortable conditions for being outdoors all day.
November in Rockville averages a daily high of 14.2°C with nights around 2.8°C. Expect roughly 9 wet days totalling 81.1mm. Generally workable, with some weather to plan around.
December in Rockville averages a daily high of 9.1°C with nights around -1.1°C. Expect roughly 10.3 wet days totalling 97mm. 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. Rockville peaks at 81.
Based on 30 years of records, April–May scores highest for comfort in Rockville, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 32°C.
July is the wettest, averaging 126.9mm of rain across roughly 9.8 wet days.
January is the coolest month, with average daily highs around 7°C.