Updated October 2026
San Juan Island National Historical Park Weather by Month
San Juan Island National Historical Park is warmest in August, when the nearest NOAA climate station averages a high of 73°F and a low of 50°F, and coldest in February, with an average high of 49°F and an average low of 37°F. November is the wettest month, with about 3 inches of precipitation.
These figures are NOAA's 1991–2020 climate normals, the 30-year average for each calendar month, from the nearest long-record weather station, 1.7 miles from the park's reference point. A single station cannot describe a whole park: temperatures elsewhere in San Juan Island National Historical Park can differ from these, particularly with elevation.
Warmest month
Aug
73°F avg high
Coldest month
Feb
37°F avg low
Wettest month
Nov
3.0 in avg
Longest days
Jun
15.9 h of daylight
Average weather at San Juan Island by month
| Month | Avg high | Avg low | Precipitation | Daylight |
|---|---|---|---|---|
| January | 47°F | 37°F | 2.7 in | 8.5 h |
| February | 49°F | 37°F | 1.5 in | 9.9 h |
| March | 53°F | 38°F | 1.4 in | 11.6 h |
| April | 57°F | 41°F | 1.0 in | 13.4 h |
| May | 64°F | 44°F | 1.1 in | 15.0 h |
| June | 68°F | 48°F | 0.8 in | 15.9 h |
| July | 72°F | 50°F | 0.5 in | 15.5 h |
| August | 73°F | 50°F | 0.7 in | 14.1 h |
| September | 68°F | 48°F | 1.0 in | 12.3 h |
| October | 59°F | 44°F | 2.3 in | 10.5 h |
| November | 51°F | 40°F | 3.0 in | 8.9 h |
| December | 46°F | 37°F | 2.5 in | 8.1 h |
| Year total | 18.5 in |
NOAA 1991–2020 climate normals from station USW00094276, 1.7 miles from the park's reference point. Daylight is the monthly average, computed from the park's latitude. Each month links to how crowded San Juan Island is at that time of year.
San Juan Island weather by season
Winter: December to February
Average highs climb from 46°F in December to 49°F in February, with average lows near 37°F. Together the three months average 6.7 inches of precipitation, about 36% of the yearly total and more than in any other season. Daylight is at its shortest, about 8.1 hours in December.
Spring: March to May
Average highs climb from 53°F in March to 64°F in May, with average lows between 38°F and 44°F. Together the three months average 3.5 inches of precipitation, about 19% of the yearly total. Daylight lengthens from about 11.6 hours in March to 15.0 in May.
Summer: June to August
Average highs climb from 68°F in June to 73°F in August, with average lows near 49°F. Together the three months average 2 inches of precipitation, about 11% of the yearly total and less than in any other season. Daylight is at its longest, about 15.9 hours in June.
Fall: September to November
Average highs fall from 68°F in September to 51°F in November, with average lows between 40°F and 48°F. Together the three months average 6.3 inches of precipitation, about 34% of the yearly total. Daylight shortens from about 12.3 hours in September to 8.9 in November.
What the National Park Service says about the weather
Spring: Temperatures usually range from 40 F to 60 F. Wildflowers are at their peak around May. Summer: Temperatures usually range from 45 F to 70 F. On very sunny days, be prepared with water-heat exhaustion is a common complaint among park visitors who are unprepared. Fall: Temperatures usually range from 40 F to 65 F. Rain is common. Winter: Temperatures range from 35 F to 50 F. Be prepared with cold and wet weather gear and numerous layers if you intend to be outside. Rain and wind are common.
Weather description courtesy of the National Park Service — official park site.
Today's forecast for San Juan Island
Averages describe a typical month, not this week. For current conditions and the seven-day outlook, the National Weather Service issues a forecast for the park's reference point at 48.51°N, 123.06°W. It covers that one spot, so other elevations in the park can differ from it, as they do from the averages above.
National Weather Service forecast for San Juan Island National Historical Park →
Weather and crowds together
August, the warmest month, sees about 1.7× the visitors of the park's average month. July is the busiest month of the year and January the quietest. To see those crowds set against the weather for all twelve months, read the best time to visit San Juan Island National Historical Park. For hotels, cabins and rentals close to the park, see where to stay near San Juan Island.
Where to stay near San Juan Island
Picked a month for San Juan Island National Historical Park? Compare hotels, cabins and vacation rentals near the park with live availability and prices.
Top-rated places to stay near San Juan Island
Prices for Oct 16–18, 4 adults. Change dates on the map below.
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Frequently Asked Questions
August is the warmest month at San Juan Island National Historical Park, with an average high of 73°F and an average low of 50°F. That is the 1991–2020 average at the nearest long-record NOAA station, 1.7 miles from the park's reference point. Temperatures inside the park can differ, particularly with elevation.
February is the coldest month at San Juan Island National Historical Park, with an average low of 37°F and an average high of 49°F, based on NOAA 1991–2020 climate normals.
November is the wettest month, with about 3 inches of precipitation. July is the driest, at about 0.5 inches. The station records about 18.5 inches of precipitation in an average year.
Daylight at San Juan Island National Historical Park runs from about 8.1 hours a day in December to about 15.9 hours in June, computed from the park's latitude.
Weather at nearby parks
56 mi away · warmest in August (75°F)
72 mi away · warmest in August (77°F)
86 mi away · warmest in August (79°F)
130 mi away · warmest in August (64°F)
Keep exploring
Sources: NOAA NCEI U.S. Climate Normals 1991–2020 (station USW00094276), daylight computed from latitude, weather description from the National Park Service, crowd levels from National Park Service Visitor Use Statistics (1979–2025). Updated 2026-10-11. Lodging results are provided by Stay22; WhenToVisitParks may earn a commission from bookings, at no extra cost to you.