| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 7.9° | 1.5° | 55.3mm | 14.5 | 32 |
| February | 9.1° | 1.9° | 46.9mm | 13.3 | 38 |
| March | 11.4° | 2.8° | 38.2mm | 12 | 48 |
| April | 14.5° | 4° | 35.4mm | 10.2 | 62 |
| May | 17.8° | 7.2° | 45.7mm | 10.6 | 72 |
| June | 20.9° | 10.1° | 46.9mm | 9.7 | 81 |
| July | 23.4° | 12.2° | 45.7mm | 10.7 | 79 |
| August | 23.1° | 12.3° | 51.1mm | 10.4 | 79 |
| September | 20.1° | 10° | 44.5mm | 9.9 | 80 |
| October | 15.7° | 7.6° | 62.8mm | 13.5 | 59 |
| November | 11° | 4° | 63.5mm | 14.7 | 42 |
| December | 8.3° | 2° | 57mm | 15.1 | 33 |
January in Brentwood averages a daily high of 7.9°C with nights around 1.5°C. Expect roughly 14.5 wet days totalling 55.3mm. A hard month to visit for comfort alone.
February in Brentwood averages a daily high of 9.1°C with nights around 1.9°C. Expect roughly 13.3 wet days totalling 46.9mm. Demanding conditions — pack for it and plan indoor options.
March in Brentwood averages a daily high of 11.4°C with nights around 2.8°C. Expect roughly 12 wet days totalling 38.2mm. Demanding conditions — pack for it and plan indoor options.
April in Brentwood averages a daily high of 14.5°C with nights around 4°C. Expect roughly 10.2 wet days totalling 35.4mm. Generally workable, with some weather to plan around.
May in Brentwood averages a daily high of 17.8°C with nights around 7.2°C. Expect roughly 10.6 wet days totalling 45.7mm. Generally workable, with some weather to plan around.
June in Brentwood averages a daily high of 20.9°C with nights around 10.1°C. Expect roughly 9.7 wet days totalling 46.9mm. Comfortable conditions for being outdoors all day.
July in Brentwood averages a daily high of 23.4°C with nights around 12.2°C. Expect roughly 10.7 wet days totalling 45.7mm. Comfortable conditions for being outdoors all day.
August in Brentwood averages a daily high of 23.1°C with nights around 12.3°C. Expect roughly 10.4 wet days totalling 51.1mm. Comfortable conditions for being outdoors all day.
September in Brentwood averages a daily high of 20.1°C with nights around 10°C. Expect roughly 9.9 wet days totalling 44.5mm. Comfortable conditions for being outdoors all day.
October in Brentwood averages a daily high of 15.7°C with nights around 7.6°C. Expect roughly 13.5 wet days totalling 62.8mm. Generally workable, with some weather to plan around.
November in Brentwood averages a daily high of 11°C with nights around 4°C. Expect roughly 14.7 wet days totalling 63.5mm. Demanding conditions — pack for it and plan indoor options.
December in Brentwood averages a daily high of 8.3°C with nights around 2°C. Expect roughly 15.1 wet days totalling 57mm. 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. Brentwood peaks at 81.
Based on 30 years of records, June–September scores highest for comfort in Brentwood, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 23.4°C.
November is the wettest, averaging 63.5mm of rain across roughly 14.7 wet days.
January is the coolest month, with average daily highs around 7.9°C.