This weather has a price Keeping the median San Juan County home comfortable runs roughly $269 a year in heating and cooling alone. See where it lands in the monthly bill

30-year climate normals

San Juan County Climate and Weather Averages

Hottest month: August

73.3°

average daily high. The coldest month is February, averaging a low of 36.5°F.

San Juan County gets 18.47" of precipitation a year, and 44% of it falls in Nov, Dec, Jan.

Temperature through the year

Each bar spans the average daily low to the average daily high for that month.

Month	Avg high	Avg low	Precip
January	47.1°	37.1°	2.69"
February	48.5°	36.5°	1.54"
March	52.6°	38.4°	1.35"
April	57.4°	40.7°	1.01"
May	63.7°	44.3°	1.14"
June	68.4°	48.1°	0.75"
July	72.4°	50.0°	0.48"
August	73.3°	50.0°	0.70"
September	68.1°	47.9°	1.04"
October	58.5°	44.0°	2.34"
November	51.0°	39.8°	2.98"
December	46.3°	36.8°	2.45"

Rainfall by month

Precipitation is spread fairly evenly through the year here, with 44% falling in the wettest three months (Nov, Dec, Jan).

January 2.69"

February 1.54"

March 1.35"

April 1.01"

May 1.14"

June 0.75"

July 0.48"

August 0.70"

September 1.04"

October 2.34"

November 2.98"

December 2.45"

Annual total 18.47"

What this climate costs you

Degree days measure how hard a building has to work to stay comfortable. They are the reason two identical houses have very different power bills, and they are the link between the weather here and what you pay every month.

Cooling degree days How much air conditioning the climate demands 32

Heating degree days How much heating the climate demands 5,171

Approximate annual cooling cost At 14.63¢/kWh, Washington average $5

Approximate annual electric heating cost Lower where heating is gas rather than electric $265

These are rough planning figures from degree days and the state electricity price, not a bill estimate. House size, insulation and fuel type move them a lot. See the full cost of owning a home in San Juan County, where electricity is one line of eight.

Common questions

What is the weather like in San Juan County?

San Juan County averages a high of 73.3°F in August and a low of 36.5°F in February. Annual precipitation is 18.47 inches, with essentially no snow.

When is the rainy season in San Juan County?

The wettest stretch is Nov, Dec, Jan, which accounts for 44% of the year's precipitation. Precipitation is relatively evenly distributed across the year.

How hot does it get in San Juan County?

The average daily high in August, the hottest month, is 73.3°F. That drives 32 cooling degree days a year, which is what your air conditioning has to work against.

Does it snow in San Juan County?

The weather station used for San Juan County, FRIDAY HARBOR AP, WA US, reports temperature and precipitation but not snowfall, so there is no snow normal to quote here. Precipitation that falls as snow is still counted in the 18.47 inches above, measured as melted water.

Sources

Temperature, precipitation and snowfall normals: NOAA National Centers for Environmental Information, 1991 to 2020 Monthly Climate Normals, station FRIDAY HARBOR AP, WA US (USW00094276), 3.8 miles from the county centroid.
Heating and cooling degree days: NOAA, same station and period.
Annual figures on this page are the sum of that station's twelve monthly normals. NOAA also publishes a separately-computed annual normal, which can differ from the monthly sum by a few percent; we use the monthly series because the month-by-month breakdown above has to come from it.
Electricity price: US Energy Information Administration, Electric Power Monthly Table 5.6.A, Washington residential average.
Wet-season share is the wettest three consecutive months as a percentage of annual precipitation, calculated from the monthly normals.