| Month | High | Low | Rain | Wet days | Score |
|---|---|---|---|---|---|
| January | 7.1° | -9.6° | 13.2mm | 4.1 | 36 |
| February | 7.9° | -9° | 17.6mm | 5.4 | 35 |
| March | 12.8° | -4.7° | 37.2mm | 5.6 | 56 |
| April | 17.3° | -0.1° | 53.2mm | 7.2 | 74 |
| May | 22.4° | 5.8° | 73.3mm | 10.3 | 79 |
| June | 28.5° | 10.5° | 50.9mm | 8.6 | 77 |
| July | 32.5° | 13.9° | 35.1mm | 7 | 64 |
| August | 31.3° | 12.6° | 35.1mm | 7.7 | 67 |
| September | 26.9° | 7.8° | 32.3mm | 6.5 | 87 |
| October | 19° | 0.5° | 19.8mm | 4.8 | 85 |
| November | 12.1° | -4.5° | 19.7mm | 4.7 | 56 |
| December | 8.6° | -8.2° | 8.6mm | 2.6 | 43 |
January in Longmont averages a daily high of 7.1°C with nights around -9.6°C. Expect roughly 4.1 wet days totalling 13.2mm. Demanding conditions — pack for it and plan indoor options.
February in Longmont averages a daily high of 7.9°C with nights around -9°C. Expect roughly 5.4 wet days totalling 17.6mm. Demanding conditions — pack for it and plan indoor options.
March in Longmont averages a daily high of 12.8°C with nights around -4.7°C. Expect roughly 5.6 wet days totalling 37.2mm. Generally workable, with some weather to plan around.
April in Longmont averages a daily high of 17.3°C with nights around -0.1°C. Expect roughly 7.2 wet days totalling 53.2mm. Generally workable, with some weather to plan around.
May in Longmont averages a daily high of 22.4°C with nights around 5.8°C. Expect roughly 10.3 wet days totalling 73.3mm. Comfortable conditions for being outdoors all day.
June in Longmont averages a daily high of 28.5°C with nights around 10.5°C. Expect roughly 8.6 wet days totalling 50.9mm. Comfortable conditions for being outdoors all day.
July in Longmont averages a daily high of 32.5°C with nights around 13.9°C. Expect roughly 7 wet days totalling 35.1mm. Generally workable, with some weather to plan around.
August in Longmont averages a daily high of 31.3°C with nights around 12.6°C. Expect roughly 7.7 wet days totalling 35.1mm. Generally workable, with some weather to plan around.
September in Longmont averages a daily high of 26.9°C with nights around 7.8°C. Expect roughly 6.5 wet days totalling 32.3mm. Comfortable conditions for being outdoors all day.
October in Longmont averages a daily high of 19°C with nights around 0.5°C. Expect roughly 4.8 wet days totalling 19.8mm. Comfortable conditions for being outdoors all day.
November in Longmont averages a daily high of 12.1°C with nights around -4.5°C. Expect roughly 4.7 wet days totalling 19.7mm. Generally workable, with some weather to plan around.
December in Longmont averages a daily high of 8.6°C with nights around -8.2°C. Rain is rare — about 2.6 wet days and 8.6mm across the month. 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. Longmont peaks at 87.
Based on 30 years of records, September–October scores highest for comfort in Longmont, balancing daytime temperature against rainfall.
July is the warmest, averaging a daily high of 32.5°C.
May is the wettest, averaging 73.3mm of rain across roughly 10.3 wet days.
January is the coolest month, with average daily highs around 7.1°C.