Waterloo, Iowa Climate by Month
Waterloo, Iowa, United States
Warm summers and freezing winters, with rain spread through the year.
The climate in Waterloo is one of warm summers and freezing winters, with rain spread through the year. Expect highs of 85°F (30°C) in July and 28°F (-2°C) in January, with the coldest nights (January) near 10°F (-12°C). About 35 in (901 mm) of rain falls in a typical year, with no clear rainy season.
- Warmest month
- 85°F(30°C)
- Average high, July
- Coldest nights
- 10°F(-12°C)
- Average low, January
- Rain per year
- 35 in(901 mm)
- No clear rainy season
- Humidity
- 75%
- Sunniest: July
Best and worst months in Waterloo
Best for weatherThe most comfortable weather comes in September, with highs around 76°F (25°C) and about 3.3 in (85 mm) of rain a month.
Least pleasantJanuary is the least pleasant month: it's the coldest, with highs of only 28°F (-2°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)
Waterloo weather by month
| Month | High | Low | Rain | Humidity | Sun |
|---|---|---|---|---|---|
| JanJanuary | 28°F(-2°C) | 10°F(-12°C) | 0.9 in(22 mm) | 85% | 1.5 |
| FebFebruary | 33°F(1°C) | 15°F(-10°C) | 1.2 in(30 mm) | 92% | 2.5 |
| MarMarch | 47°F(8°C) | 27°F(-3°C) | 2.2 in(55 mm) | 67% | 3.7 |
| AprApril | 60°F(16°C) | 38°F(3°C) | 3.9 in(99 mm) | 59% | 4.5 |
| MayMay | 72°F(22°C) | 49°F(10°C) | 4.7 in(120 mm) | 66% | 5.2 |
| JunJune | 82°F(28°C) | 60°F(15°C) | 5.0 in(128 mm) | 70% | 5.8 |
| JulJuly | 85°F(30°C) | 63°F(17°C) | 4.5 in(114 mm) | 73% | 6.0 |
| AugAugust | 83°F(28°C) | 61°F(16°C) | 3.8 in(96 mm) | 75% | 5.3 |
| SepSeptemberBest | 76°F(25°C) | 52°F(11°C) | 3.3 in(85 mm) | 68% | 4.4 |
| OctOctober | 62°F(17°C) | 40°F(5°C) | 2.8 in(70 mm) | 70% | 2.8 |
| NovNovember | 46°F(8°C) | 28°F(-2°C) | 1.8 in(45 mm) | 80% | 1.8 |
| DecDecember | 33°F(0°C) | 17°F(-9°C) | 1.5 in(37 mm) | 89% | 1.3 |
1991–2020 averages. Sun is solar radiation in kWh/m² per day. Highlighted: the most comfortable months.
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