Mercer Island Weather in December

December in Mercer Island sees daytime temperatures around 8°C (46°F) and lows of 2°C (36°F) at night. With around 154 mm (6.1 in) of rainfall expected, it's worth packing a rain jacket.

Rainfall in Mercer Island in December

This month experiences about 20 days of rain according to historical data, averaging 154 mm (6.1 in). This is a wet month with frequent and often heavy showers. Both the number of rain days and the total rainfall are high.

Temperature in Mercer Island in December

In December, Mercer Island gets low temperatures, with highs of 8°C (46°F). Nights cool to around 2°C (36°F). The winter season takes place during December. It stays cool throughout the day, so warm layers are a good idea from morning to evening. Nights drop to 2°C (36°F). Cold nights like these are actually great for sleeping well, as long as you have a warm enough duvet. Expect the coldest temperatures of the year this month. Make sure you have enough winter clothing to stay warm.

Sunshine in Mercer Island in December

The area experiences limited sunny days, amounting to roughly 54 hours of sunshine. This makes it perfect for those who lean towards cooler, cloudier settings rather than intense sunlit days.

Wind Speed in Mercer Island in December

In December, average wind speeds reach 4 m/s (8 knots), leading to light to moderate breezes. Conditions vary from day to day, with both calm and windier periods.

If you prefer dry days with pleasant temperatures, December may not be the ideal month to visit Mercer Island. Our weather planner can help you explore destinations with more pleasant weather conditions.