Crystal Lake Climate by Month
Crystal Lake, Illinois, United States
Warm summers and freezing winters, with rain spread through the year.
Crystal Lake has warm summers and freezing winters, with rain spread through the year. July is the warmest month, with highs around 84°F (29°C); January is the coolest at 30°F (-1°C), and nights dip to 14°F (-10°C). About 38 in (960 mm) of rain falls in a typical year, with no clear rainy season.
- Warmest month
- 84°F(29°C)
- Average high, July
- Coldest nights
- 14°F(-10°C)
- Average low, January
- Rain per year
- 38 in(960 mm)
- No clear rainy season
- Humidity
- 73%
- Sunniest: July
Best and worst months in Crystal Lake
Best for weatherSeptember is the best time for weather in Crystal Lake: highs near 75°F (24°C) and about 3.8 in (96 mm) of rain a month.
Least pleasantJanuary is the least pleasant month: it's the coldest, with highs of only 30°F (-1°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)
Crystal Lake weather by month
| Month | High | Low | Rain | Humidity | Sun |
|---|---|---|---|---|---|
| JanJanuary | 30°F(-1°C) | 14°F(-10°C) | 1.7 in(44 mm) | 98% | 1.4 |
| FebFebruary | 35°F(2°C) | 17°F(-8°C) | 1.5 in(38 mm) | 83% | 2.5 |
| MarMarch | 47°F(8°C) | 28°F(-2°C) | 2.3 in(58 mm) | 67% | 3.6 |
| AprApril | 58°F(15°C) | 37°F(3°C) | 4.2 in(106 mm) | 62% | 4.5 |
| MayMay | 71°F(21°C) | 47°F(9°C) | 4.4 in(112 mm) | 65% | 5.1 |
| JunJune | 80°F(27°C) | 57°F(14°C) | 4.6 in(116 mm) | 71% | 5.8 |
| JulJuly | 84°F(29°C) | 62°F(17°C) | 3.9 in(98 mm) | 68% | 5.9 |
| AugAugust | 82°F(28°C) | 61°F(16°C) | 4.3 in(108 mm) | 73% | 5.1 |
| SepSeptemberBest | 75°F(24°C) | 53°F(12°C) | 3.8 in(96 mm) | 69% | 4.3 |
| OctOctober | 63°F(17°C) | 41°F(5°C) | 2.8 in(71 mm) | 68% | 2.7 |
| NovNovember | 47°F(9°C) | 30°F(-1°C) | 2.4 in(62 mm) | 75% | 1.7 |
| DecDecember | 35°F(2°C) | 20°F(-7°C) | 2.0 in(51 mm) | 79% | 1.3 |
1991–2020 averages. Sun is solar radiation in kWh/m² per day. Highlighted: the most comfortable months.
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