Last updated: June 24, 2025
In Grinnell, United States, the average temperature in December hovers around -1°C (31°F). While temperatures can dip to a chilling -23°C (-8°F), they can also reach a pleasant 23°C (73°F). Expect 38 mm (1.5 in) of precipitation spread over 5 days and an average humidity level of 83% that adds to the overall atmosphere of the region.
In December in Grinnell, the average temperature is -1°C (31°F), with maximums reaching 23°C (73°F) and minimums plummeting as low as -23°C (-8°F). Travelers should be prepared for a wide range of temperatures, from chilly conditions requiring warm clothing to occasional mild days suitable for outdoor activities.
In Grinnell in December, the total precipitation amount is 38 mm (1.5 in) spread over a duration of 5 days.
In Grinnell in December humidity is 83%. With an average temperature of -1°C (31°F), this humidity feels like a heavy, icy blanket enveloping you, making each step outside feel like a struggle against the cold, damp air that clings to your skin, often leaving you wishing for warmth and refuge indoors.
In Grinnell in December, the maximum UV index is 3, which corresponds to a moderate Exposure Category. The time to burn is approximately 30 minutes. For more details on the hourly UV index in Grinnell, you can check the information here.
UV Risk Categories
Weather in Grinnell varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Grinnell, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -6°C (22°F) | 43 mm (1.7 inches) | 78% | moderate |
| February Weather | -5°C (23°F) | 48 mm (1.9 inches) | 80% | moderate |
| March Weather | 4°C (39°F) | 79 mm (3.1 inches) | 77% | high |
| April Weather | 9°C (49°F) | 81 mm (3.2 inches) | 77% | very high |
| May Weather | 17°C (62°F) | 166 mm (6.5 inches) | 77% | very high |
| June Weather | 23°C (74°F) | 133 mm (5.2 inches) | 81% | extreme |
| July Weather | 24°C (76°F) | 81 mm (3.2 inches) | 81% | very high |
| August Weather | 23°C (73°F) | 71 mm (2.8 inches) | 77% | very high |
| September Weather | 20°C (68°F) | 118 mm (4.7 inches) | 73% | very high |
| October Weather | 11°C (53°F) | 145 mm (5.7 inches) | 75% | high |
| November Weather | 3°C (38°F) | 46 mm (1.8 inches) | 85% | moderate |
| December Weather | -1°C (31°F) | 38 mm (1.5 inches) | 83% | moderate |