Last updated: June 24, 2025
In December, the average temperature in Hayward, United States hovers around -6°C (21°F). During this month, temperatures can dip as low as -32°C (-26°F), while occasionally reaching a high of 14°C (58°F). Expect 61 mm (2.4 in) of precipitation spread across about 9 days, and don't forget the 85% average humidity that can make the chill feel even more intense.
In December in Hayward, the average temperature is -6°C (21°F). The maximum can reach 14°C (58°F), while the minimum can drop as low as -32°C (-26°F). Be prepared for a wide range of temperatures when traveling during this month, and pack accordingly for both chilly days and potential warmer spells.
In Hayward in December, the precipitation amount is 61 mm (2.4 in) spread over 9 days.
In Hayward in December, humidity is 85%. With an average temperature of -6°C (21°F), this humidity feels like a damp chill that seeps into your bones, making travel uncomfortable and forcing you to bundle up even more than usual as you navigate through frosty air.
In Hayward 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 Hayward, you can visit Hourly UV Index in Hayward.
UV Risk Categories
Weather in Hayward varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Hayward, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -10°C (14°F) | 26 mm (1.0 inches) | 88% | low |
| February Weather | -10°C (15°F) | 40 mm (1.6 inches) | 89% | moderate |
| March Weather | -2°C (29°F) | 49 mm (1.9 inches) | 86% | moderate |
| April Weather | 4°C (40°F) | 88 mm (3.5 inches) | 85% | high |
| May Weather | 13°C (56°F) | 104 mm (4.1 inches) | 79% | very high |
| June Weather | 19°C (67°F) | 94 mm (3.7 inches) | 80% | very high |
| July Weather | 22°C (71°F) | 100 mm (3.9 inches) | 80% | very high |
| August Weather | 20°C (68°F) | 113 mm (4.5 inches) | 78% | very high |
| September Weather | 16°C (61°F) | 104 mm (4.1 inches) | 80% | high |
| October Weather | 8°C (46°F) | 94 mm (3.7 inches) | 84% | moderate |
| November Weather | -1°C (31°F) | 46 mm (1.8 inches) | 89% | moderate |
| December Weather | -6°C (21°F) | 61 mm (2.4 inches) | 85% | low |