Longmont Climate by Month
Longmont, Colorado, United States
Hot summers and cold winters, with rain spread through the year.
Hot summers and cold winters, with rain spread through the year: that's Longmont's climate in short. Expect highs of 90°F (32°C) in July and 46°F (8°C) in December, with the coldest nights (January) near 15°F (-9°C). About 15 in (375 mm) of rain falls in a typical year, with no clear rainy season.
- Warmest month
- 90°F(32°C)
- Average high, July
- Coldest nights
- 15°F(-9°C)
- Average low, January
- Rain per year
- 15 in(375 mm)
- No clear rainy season
- Humidity
- 47%
- Sunniest: July
Best and worst months in Longmont
Best for weatherThe most comfortable weather comes in May and September, with highs around 76°F (25°C) and about 1.9 in (48 mm) of rain a month.
Least pleasantDecember and January are the least pleasant; December is the coldest, with highs of only 46°F (8°C).
Comfort combines how close the afternoon high is to 75°F (24°C) with how much rain falls and how humid it is. See where the weather is best in September.
Temperature and rain through the year
Highs and lows (°F)
Average highAverage low
Rain (in per month)
Longmont weather by month
| Month | High | Low | Rain | Humidity | Sun |
|---|---|---|---|---|---|
| JanJanuary | 46°F(8°C) | 15°F(-9°C) | 0.5 in(12 mm) | 52% | 2.3 |
| FebFebruary | 48°F(9°C) | 18°F(-8°C) | 0.5 in(13 mm) | 47% | 3.2 |
| MarMarch | 57°F(14°C) | 26°F(-3°C) | 1.3 in(33 mm) | 45% | 4.6 |
| AprApril | 64°F(18°C) | 34°F(1°C) | 1.9 in(47 mm) | 42% | 5.4 |
| MayMayBest | 73°F(23°C) | 43°F(6°C) | 2.4 in(62 mm) | 49% | 6.3 |
| JunJune | 84°F(29°C) | 52°F(11°C) | 1.7 in(42 mm) | 43% | 7.0 |
| JulJuly | 90°F(32°C) | 57°F(14°C) | 1.7 in(43 mm) | 42% | 7.0 |
| AugAugust | 87°F(31°C) | 55°F(13°C) | 1.3 in(32 mm) | 46% | 6.1 |
| SepSeptemberBest | 80°F(27°C) | 46°F(8°C) | 1.3 in(33 mm) | 46% | 5.2 |
| OctOctober | 67°F(19°C) | 34°F(1°C) | 1.1 in(27 mm) | 48% | 3.6 |
| NovNovember | 54°F(12°C) | 24°F(-5°C) | 0.8 in(20 mm) | 50% | 2.5 |
| DecDecember | 46°F(8°C) | 16°F(-9°C) | 0.4 in(11 mm) | 52% | 2.1 |
1991–2020 averages. Sun is solar radiation in kWh/m² per day. Highlighted: the most comfortable months.
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