Last updated: June 24, 2025
In December, the average temperature in Swansea, United States hovers around 4°C (40°F), with extremes ranging from a chilly -16°C (3°F) to a mild 23°C (73°F). Expect a total precipitation of 67 mm (2.7 in) over an average of 7 days, contributing to a high average humidity of 86%. Whether you're braving the cold or enjoying the rare warmth, be prepared for a month of diverse weather!
In December in Swansea, the average temperature is 4°C (40°F). Maximum can reach 23°C (73°F) and minimum can be as low as -16°C (3°F). This wide range of temperatures means travelers should prepare for varying weather conditions, so layers and warm clothing are advisable.
In Swansea in December, the precipitation amount is 67 mm (2.7 in) over a span of 7 days.
In Swansea in December humidity is 86%. With an average temperature of 4°C (40°F), this humidity feels like a damp chill that seeps into your bones, making outdoor activities uncomfortable and travel cumbersome as you navigate through a thick, heavy air that clings to your skin.
In Swansea 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 Swansea, you can check the information here.
UV Risk Categories
Weather in Swansea varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Swansea, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | 1°C (33°F) | 80 mm (3.2 inches) | 82% | moderate |
| February Weather | 2°C (36°F) | 83 mm (3.3 inches) | 80% | moderate |
| March Weather | 9°C (48°F) | 139 mm (5.5 inches) | 80% | high |
| April Weather | 13°C (56°F) | 148 mm (5.8 inches) | 80% | very high |
| May Weather | 20°C (68°F) | 158 mm (6.2 inches) | 82% | very high |
| June Weather | 25°C (77°F) | 100 mm (4.0 inches) | 83% | extreme |
| July Weather | 27°C (80°F) | 91 mm (3.6 inches) | 81% | very high |
| August Weather | 25°C (77°F) | 129 mm (5.1 inches) | 80% | very high |
| September Weather | 23°C (73°F) | 59 mm (2.3 inches) | 76% | very high |
| October Weather | 15°C (60°F) | 107 mm (4.2 inches) | 76% | high |
| November Weather | 7°C (45°F) | 77 mm (3.0 inches) | 85% | moderate |
| December Weather | 4°C (40°F) | 67 mm (2.7 inches) | 86% | moderate |