Last updated: June 24, 2025
In December, the average temperature in Johnston, United States hovers around 2°C (36°F), with a minimum dipping to -16°C (4°F) and a maximum reaching up to 17°C (63°F). Expect about 121 mm (4.8 in) of precipitation spread across 10 days, and prepare for a relatively high average humidity of 80%.
In December in Johnston, the average temperature is 2°C (36°F). The maximum can reach 17°C (63°F), while the minimum can drop as low as -16°C (4°F). Travelers should be prepared for a wide range of temperatures, making layered clothing essential for comfort during their visit.
In Johnston in December, the precipitation amount is 121 mm (4.8 in) spread over a period of 10 days.
In Johnston in December humidity is 80%. With an average temperature of 2°C (36°F), this humidity feels like a heavy, damp chill that seeps into your bones, making it challenging for outdoor adventures and often necessitating layered clothing to stay warm and comfortable while exploring.
In Johnston in December, the maximum UV index is 2, which corresponds to a low exposure category. With this level of UV radiation, the time to burn is approximately 45 minutes. To learn more about the hourly UV index in Johnston, you can visit Hourly UV Index in Johnston.
UV Risk Categories
Weather in Johnston varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Johnston, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | 0°C (32°F) | 73 mm (2.9 inches) | 84% | moderate |
| February Weather | 1°C (34°F) | 90 mm (3.5 inches) | 84% | moderate |
| March Weather | 4°C (39°F) | 99 mm (3.9 inches) | 82% | high |
| April Weather | 9°C (49°F) | 127 mm (5.0 inches) | 79% | very high |
| May Weather | 15°C (59°F) | 103 mm (4.1 inches) | 75% | very high |
| June Weather | 20°C (68°F) | 98 mm (3.8 inches) | 78% | very high |
| July Weather | 23°C (74°F) | 130 mm (5.1 inches) | 76% | very high |
| August Weather | 23°C (74°F) | 101 mm (4.0 inches) | 76% | very high |
| September Weather | 19°C (67°F) | 93 mm (3.7 inches) | 75% | very high |
| October Weather | 14°C (57°F) | 133 mm (5.3 inches) | 75% | high |
| November Weather | 7°C (44°F) | 99 mm (3.9 inches) | 80% | moderate |
| December Weather | 2°C (36°F) | 121 mm (4.8 inches) | 80% | low |