| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 7.2° | 1.2° | 66.8mm | 16 | 28 |
| February | 8.3° | 1.8° | 54.5mm | 13.8 | 35 |
| March | 10.6° | 2.7° | 46mm | 12.9 | 44 |
| April | 13.7° | 4.3° | 46.7mm | 11.6 | 57 |
| May | 16.8° | 7.4° | 50.4mm | 11.6 | 67 |
| June | 20° | 10.3° | 48.6mm | 10.5 | 79 |
| July | 22.3° | 12.3° | 53.3mm | 10.9 | 78 |
| August | 21.9° | 12.4° | 64.1mm | 11.8 | 76 |
| September | 18.9° | 10.4° | 56.2mm | 11.5 | 73 |
| October | 14.8° | 7.8° | 79.1mm | 15.4 | 53 |
| November | 10.3° | 4° | 77.2mm | 17.1 | 39 |
| December | 7.7° | 2° | 67.6mm | 16.3 | 31 |
January in Welwyn Garden City averages a daily high of 7.2°C with nights around 1.2°C. Expect roughly 16 wet days totalling 66.8mm. A hard month to visit for comfort alone.
February in Welwyn Garden City averages a daily high of 8.3°C with nights around 1.8°C. Expect roughly 13.8 wet days totalling 54.5mm. Demanding conditions — pack for it and plan indoor options.
March in Welwyn Garden City averages a daily high of 10.6°C with nights around 2.7°C. Expect roughly 12.9 wet days totalling 46mm. Demanding conditions — pack for it and plan indoor options.
April in Welwyn Garden City averages a daily high of 13.7°C with nights around 4.3°C. Expect roughly 11.6 wet days totalling 46.7mm. Generally workable, with some weather to plan around.
May in Welwyn Garden City averages a daily high of 16.8°C with nights around 7.4°C. Expect roughly 11.6 wet days totalling 50.4mm. Generally workable, with some weather to plan around.
June in Welwyn Garden City averages a daily high of 20°C with nights around 10.3°C. Expect roughly 10.5 wet days totalling 48.6mm. Comfortable conditions for being outdoors all day.
July in Welwyn Garden City averages a daily high of 22.3°C with nights around 12.3°C. Expect roughly 10.9 wet days totalling 53.3mm. Comfortable conditions for being outdoors all day.
August in Welwyn Garden City averages a daily high of 21.9°C with nights around 12.4°C. Expect roughly 11.8 wet days totalling 64.1mm. Comfortable conditions for being outdoors all day.
September in Welwyn Garden City averages a daily high of 18.9°C with nights around 10.4°C. Expect roughly 11.5 wet days totalling 56.2mm. Generally workable, with some weather to plan around.
October in Welwyn Garden City averages a daily high of 14.8°C with nights around 7.8°C. Expect roughly 15.4 wet days totalling 79.1mm. Demanding conditions — pack for it and plan indoor options.
November in Welwyn Garden City averages a daily high of 10.3°C with nights around 4°C. Expect roughly 17.1 wet days totalling 77.2mm. Demanding conditions — pack for it and plan indoor options.
December in Welwyn Garden City averages a daily high of 7.7°C with nights around 2°C. Expect roughly 16.3 wet days totalling 67.6mm. 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. Welwyn Garden City peaks at 79.
Based on 30 years of records, June–September scores highest for comfort in Welwyn Garden City, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 22.3°C.
October is the wettest, averaging 79.1mm of rain across roughly 15.4 wet days.
January is the coolest month, with average daily highs around 7.2°C.