| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 8.6° | -7.1° | 12.4mm | 4.2 | 41 |
| February | 9.3° | -6.7° | 16.9mm | 4.8 | 43 |
| March | 13.9° | -2.4° | 32.5mm | 5.5 | 63 |
| April | 17.9° | 1.4° | 49.8mm | 7.8 | 77 |
| May | 22.4° | 6.6° | 63.3mm | 9.8 | 80 |
| June | 29.4° | 11.8° | 37.2mm | 6.9 | 77 |
| July | 33.1° | 15° | 47.9mm | 7.7 | 60 |
| August | 31.9° | 14° | 32.2mm | 7.4 | 66 |
| September | 27.7° | 9.3° | 31.3mm | 5.6 | 86 |
| October | 20° | 2.7° | 24.6mm | 5 | 90 |
| November | 13.8° | -2.6° | 16.3mm | 4.1 | 65 |
| December | 8.9° | -6.9° | 14.3mm | 3.7 | 44 |
January in Thornton averages a daily high of 8.6°C with nights around -7.1°C. Expect roughly 4.2 wet days totalling 12.4mm. Demanding conditions — pack for it and plan indoor options.
February in Thornton averages a daily high of 9.3°C with nights around -6.7°C. Expect roughly 4.8 wet days totalling 16.9mm. Demanding conditions — pack for it and plan indoor options.
March in Thornton averages a daily high of 13.9°C with nights around -2.4°C. Expect roughly 5.5 wet days totalling 32.5mm. Generally workable, with some weather to plan around.
April in Thornton averages a daily high of 17.9°C with nights around 1.4°C. Expect roughly 7.8 wet days totalling 49.8mm. Comfortable conditions for being outdoors all day.
May in Thornton averages a daily high of 22.4°C with nights around 6.6°C. Expect roughly 9.8 wet days totalling 63.3mm. Comfortable conditions for being outdoors all day.
June in Thornton averages a daily high of 29.4°C with nights around 11.8°C. Expect roughly 6.9 wet days totalling 37.2mm. Comfortable conditions for being outdoors all day.
July in Thornton averages a daily high of 33.1°C with nights around 15°C. Expect roughly 7.7 wet days totalling 47.9mm. Generally workable, with some weather to plan around.
August in Thornton averages a daily high of 31.9°C with nights around 14°C. Expect roughly 7.4 wet days totalling 32.2mm. Generally workable, with some weather to plan around.
September in Thornton averages a daily high of 27.7°C with nights around 9.3°C. Expect roughly 5.6 wet days totalling 31.3mm. Comfortable conditions for being outdoors all day.
October in Thornton averages a daily high of 20°C with nights around 2.7°C. Expect roughly 5 wet days totalling 24.6mm. Comfortable conditions for being outdoors all day.
November in Thornton averages a daily high of 13.8°C with nights around -2.6°C. Expect roughly 4.1 wet days totalling 16.3mm. Generally workable, with some weather to plan around.
December in Thornton averages a daily high of 8.9°C with nights around -6.9°C. Expect roughly 3.7 wet days totalling 14.3mm. 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. Thornton peaks at 90.
Based on 30 years of records, September–October scores highest for comfort in Thornton, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 33.1°C.
May is the wettest, averaging 63.3mm of rain across roughly 9.8 wet days.
January is the coolest month, with average daily highs around 8.6°C.