Best Time for Outdoor Projects in Washington

Washington weather and outdoor projects

Western Washington, including Seattle, has a marine climate with mild, cloudy, damp weather from October to May and dry, mild summers. July through mid-September is the main window for staining and painting, because the rest of the year often brings long damp spells and short days.

East of the Cascades, Spokane and the Columbia Basin are much drier, with hot summers and cold winters. Moss and mildew grow readily west of the mountains, so clean decks and siding before coating them. Late-summer wildfire smoke can affect both sides of the state.

Frost dates in Washington

In Seattle, the median last spring freeze (32°F) is around March 2 and the median first fall freeze is around November 23, a frost-free season of about 266 days.

In Spokane, the median last spring freeze (32°F) is around April 26 and the median first fall freeze is around October 12, a frost-free season of about 168 days.

Frost dates matter for concrete, which must not freeze in its first 48 hours, for paint and caulk that need nights above their minimum, and for lawn care, since crabgrass preventer goes down as the soil warms in spring. See how late in fall you can stain, paint or seal.

Best time to stain a deck in Washington

In Seattle, the most reliable months are May–September. April and October can also work on the right days. November–March is too cold, with average highs around 50°F. April and October are cool, with highs around 60°F, so choose the warmest afternoons.

In Spokane, the most reliable months are June–September. May and October can also work on the right days. November–March is too cold, with average highs around 40°F. In April, nights average about 37°F, too cold for the coating to dry and cure overnight. In May, nights average about 45°F, so finish early on mild days and check the overnight low. October is cool, with highs around 58°F, so choose the warmest afternoons.

Check this week’s hour-by-hour verdict with the deck staining forecast.

Best time to paint outside in Washington

In Seattle, the most reliable months are May–September. February–April and October can also work on the right days. December–January is too cold, with average highs around 48°F. November averages about 13 days a month with a tenth of an inch of rain or more, which makes long dry stretches hard to find. February–March is cool, with highs around 52°F, so choose the warmest afternoons. In April, nights average about 43°F, so finish early on mild days and check the overnight low. October averages about 8 wet days a month, so wait for a clear stretch.

In Spokane, the most reliable months are June–September. April–May and October can also work on the right days. November–March is too cold, with average highs around 40°F. April and October are cool, with highs around 57°F, so choose the warmest afternoons. In May, nights average about 45°F, so finish early on mild days and check the overnight low.

Check this week’s hour-by-hour verdict with the exterior painting forecast.

Best time to pour concrete in Washington

In Seattle, the most reliable months are April–October. November–March can also work on the right days. November–March brings about 5 freezing nights a month, so pick a mild spell and keep curing blankets on hand.

In Spokane, the most reliable months are May–September. October can also work on the right days. November–April averages about 20 nights a month at or below 32°F, so fresh concrete needs blankets or heated enclosures. October brings about 8 freezing nights a month, so pick a mild spell and keep curing blankets on hand.

Check this week’s hour-by-hour verdict with the concrete pouring forecast.

Best time to seal a driveway in Washington

In Seattle, the most reliable months are June–September. May and October can also work on the right days. November–April is too cold, with average highs around 52°F. May and October are cool, with highs around 63°F, so choose the warmest afternoons.

In Spokane, the most reliable months are July–August. May–June and September can also work on the right days. October–April is too cold, with average highs around 45°F. May is cool, with highs around 67°F, so choose the warmest afternoons. In June and September, nights average about 50°F, so finish early on mild days and check the overnight low.

Check this week’s hour-by-hour verdict with the driveway sealing forecast.

Best time to fertilize or treat a lawn in Washington

In Seattle, the most reliable months are May–October. February–April and November can also work on the right days. December–January is too cold, with average highs around 48°F. February–April and November are cool, with highs around 54°F, so choose the warmest afternoons.

In Spokane, the most reliable months are May–September. April and October can also work on the right days. November–March is too cold, with average highs around 40°F. April and October are cool, with highs around 57°F, so choose the warmest afternoons.

Check this week’s hour-by-hour verdict with the lawn fertilizer forecast.

How the weather differs across Washington

Of the places above, Seattle has the most good months for staining, painting and concrete combined (17 job-months), and Spokane has the fewest (13). If you live between them, expect something in between, and higher ground to be cooler with a shorter season.

Monthly weather in Seattle

*Days with at least 0.1 inch of rain or melted snow. Freezing nights: average nights a month at or below 32°F. Humidity is calculated from NOAA hourly normal temperature and dew point at 3 PM.

Monthly weather in Spokane

Use the averages, then check the forecast

These ratings describe a typical month, not a particular week. A warm spell in a “poor” month can give you a good day, and a wet week can spoil a “good” one. Use this page to plan the season, then check the 7-day forecast for your ZIP code before you buy materials or book help. Each project forecast checks the hours after you finish too: overnight lows, dew and rain that would ruin fresh stain, paint, sealer or concrete.

About this data

Monthly temperatures, rain days, snowfall and freeze dates are NOAA National Centers for Environmental Information (NCEI) U.S. Climate Normals for 1991–2020 at SEATTLE TACOMA INTL AP, SPOKANE INTL AP. Ratings apply the same temperature limits as our forecasts (for example, 50°F or warmer for deck stain and driveway sealer, and no freezing nights for new concrete) to the average month. Your product label always takes priority.