Skip to content
seatemperatures.net

San Juan Islands Sea Temperature in December

Washington, United States

November San Juan Islands year-round → January

Average sea temperature for San Juan Islands, United States across December, based on 10 years of daily readings.

Average

8.21° C

High

9.85° C

Low

6.81° C

This water is very cold and can cause pain. We don't recommend you swim in this temperature for anything other than very short swims of 5 to 10 minutes unless you are a very experienced cold water swimmer.

December is the 9th warmest of 12 months at San Juan Islands. On average the water sits 2.8° than the year-round mean of 11.01° C.

Compared to November, December is 1.1° cooler than (9.3° C in November). By January the water is usually 7.58° C.

San Juan Islands Day-by-Day Water Temperature in December

10-year low, average and high

6.0° C
7.1° C
8.3° C
9.4° C
10.5° C
1
5
10
15
20
25
31
Day-by-day low and high band with the 10-year daily average through December. Range Average

Each vertical bar above is one day of December. The shaded band covers the range the water has reached on that day across the last 10 years — the lowest reading at the bottom, the highest at the top. The line running through the bars is the daily average over those 10 years, so you can see the typical shape of the month at San Juan Islands.

A narrow band means the temperature on that day has stayed close to the average year on year. A taller band means it has swung more, often because of changeable weather around that time of year. Hovering a day pulls up its low, average, and high.

December Water Temperature Table for San Juan Islands

10-year daily averages

Day Average Low High
December 1 8.72° C 8° C 9.27° C
December 2 8.63° C 7.89° C 9.31° C
December 3 8.57° C 7.88° C 9.28° C
December 4 8.54° C 7.7° C 9.85° C
December 5 8.55° C 7.74° C 9.79° C
December 6 8.48° C 7.58° C 9.35° C
December 7 8.43° C 7.78° C 9.16° C
December 8 8.48° C 7.98° C 9.2° C
December 9 8.38° C 7.91° C 9.04° C
December 10 8.32° C 7.61° C 9.12° C
December 11 8.31° C 7.49° C 9.09° C
December 12 8.28° C 7.33° C 8.82° C
December 13 8.26° C 7.39° C 8.84° C
December 14 8.26° C 7.08° C 9.2° C
December 15 8.28° C 7.02° C 9.43° C
December 16 8.27° C 7° C 9.46° C
December 17 8.27° C 7.16° C 9.41° C
December 18 8.27° C 7.22° C 9.35° C
December 19 8.29° C 7.42° C 9.24° C
December 20 8.23° C 7.35° C 9.13° C
December 21 8.1° C 7.23° C 9.1° C
December 22 8.01° C 7.06° C 9° C
December 23 7.95° C 7.01° C 8.92° C
December 24 7.87° C 6.82° C 8.94° C
December 25 7.81° C 6.85° C 8.87° C
December 26 7.86° C 6.97° C 8.86° C
December 27 7.85° C 6.99° C 8.98° C
December 28 7.86° C 6.86° C 9.3° C
December 29 7.81° C 6.84° C 9.24° C
December 30 7.83° C 7.05° C 9.23° C
December 31 7.78° C 6.81° C 9.17° C

Where December Sits in the Year

December highlighted

4.0° C
8.3° C
12.5° C
16.8° C
21.0° C
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
7.58° C
7.41° C
7.99° C
9.55° C
11.96° C
13.57° C
15.54° C
15.79° C
14.05° C
11.17° C
9.3° C
8.21° C
10-year monthly history for San Juan Islands. Bars span historical low to high; the line marks the monthly average. Range Average
January → February → March → April → May → June → July → August → September → October → November → December →

Nearby Locations in December

Compare other United States water for the same month

San Juan Islands Location

48.5514, -123.0781

48.55137, -123.07811 View on OpenStreetMap →

San Juan Islands sits at 48.5514°N, 123.0781°W, on the coast of Washington, United States. The marker on the map shows the spot the readings on this page come from. It usually sits a short distance from the town centre, out on the open water itself, so the numbers stay tied to the coast rather than a generic point inland.

Coastlines bend, headlands focus the water, and the temperature can run noticeably differently between two beaches that look close together on a map. Comparing nearby locations is a quick way to see how local geography is shaping the readings.

Nearest locations to San Juan Islands