When To Plant Squash In Washington State

The best time to plant squash in Washington State is from late May to mid-June, once the soil has warmed to at least 60°F and all danger of frost has passed. 

If you’ve been wondering when to plant squash in Washington, the short answer is: wait until your local last frost date has come and gone, then give the soil another week or two to heat up. 

Squash loves warmth, and planting too early in Washington’s cool, damp spring is the fastest way to end up with rotten seeds and sad little seedlings. 

In this post, we’ll break down exactly when to plant squash in Washington State, how your region affects the timing, and a few tips to get your crop off to a strong start. 

Let’s dig in. 

When to Plant Squash in Washington State

Squash is a warm-season crop, which means it absolutely hates cold soil. 

In Washington, that single fact drives almost every decision about when to plant squash. 

Here’s what that looks like across the state’s very different growing regions. 

1. Wait Until Soil Hits 60°F

Squash seeds won’t germinate well in soil cooler than 60°F, and they’ll simply rot if it’s below 55°F. 

In western Washington, that usually means late May or early June. 

In eastern Washington, where springs warm up faster, you might hit that mark by mid to late May. 

The smartest move is to grab a soil thermometer and check before you plant, rather than trusting the calendar alone. 

2. Watch Your Local Last Frost Date

Squash seedlings are tender and will be killed by even a light frost. 

Most of western Washington sees its last frost between late April and mid-May. 

Eastern Washington, especially in higher elevations, can see frost well into May. 

The safest rule for when to plant squash in Washington is to wait at least one to two weeks after your area’s average last frost date. 

3. Cool Nights Slow Everything Down

Even after the last frost, Washington nights can stay chilly well into June. 

Squash plants stall when nighttime temperatures drop below 50°F, so planting early rarely gives you a head start. 

You’re better off waiting for consistently warm nights than gambling on an early planting. 

That’s why late May through mid-June is the sweet spot for planting squash in Washington. 

When to Plant Squash in Washington by Region

Washington isn’t one climate, and when to plant squash depends a lot on where you live. 

Here’s a quick regional breakdown to help you time it right. 

1. Western Washington (Seattle, Tacoma, Bellingham)

Western Washington has cool, wet springs that warm up slowly. 

Your best bet for planting squash here is late May to mid-June. 

If you’re in a coastal spot, push it even later, since marine air keeps things cool. 

2. Eastern Washington (Spokane, Yakima, Tri-Cities)

Eastern Washington warms up faster, so you can often plant squash from mid to late May. 

The Tri-Cities area is the warmest, sometimes allowing planting as early as mid-May. 

Just keep an eye out for late cold snaps, which do happen. 

3. Higher Elevations and Mountain Areas

If you’re gardening in the mountains or at high elevation, everything shifts later. 

When to plant squash in these areas can stretch into late June. 

Short-season varieties and season extenders like row covers or black plastic mulch are your friends here. 

Tips for Planting Squash in Washington State

Once you’ve nailed down when to plant squash in Washington, a few smart moves will set your crop up for success. 

Here’s how to give your squash the best shot. 

1. Warm the Soil First

Squash thrives in warm soil, so give it a boost before planting. 

Black plastic mulch or clear plastic laid over the bed a couple of weeks ahead can raise soil temps significantly. 

This is especially helpful in cooler parts of western Washington. 

2. Start Seeds Indoors as a Backup

Starting squash seeds indoors two to three weeks before your target planting date works well in Washington. 

Just don’t start too early, since squash seedlings grow fast and hate being root-bound. 

Transplant them out once the soil and air are reliably warm. 

3. Choose the Right Varieties

Short-season squash varieties are a smart choice in cooler parts of the state. 

Bush types of zucchini and summer squash tend to do better in Washington’s shorter season than sprawling vining types. 

If you’re planting squash for winter storage, look for varieties that mature in 90 days or less. 

4. Protect Young Plants

Row covers or cloches can shield young squash plants from lingering cool nights. 

Just remember to remove covers once flowers appear so pollinators can get in. 

A little protection in those first few weeks makes a big difference. 

So, When to Plant Squash in Washington?

The best time to plant squash in Washington is late May to mid-June, after the last frost and once soil temperatures reach 60°F. 

Western Washington gardeners should lean toward the later end of that window, while eastern Washington gardeners can often plant a bit earlier. 

Wait for warm soil and warm nights, protect young plants, and your squash will reward you with a productive season. 

Hope this post has helped you figure out exactly when to plant squash in Washington State, no matter which corner of the state you’re gardening in.