When to Plant a Garden in Washington State: Frost-Date Rules by Region

Planting a garden in Washington State depends on your region’s last frost date — a window that shifts from late March in the Puget Sound to mid-May in Eastern WA, where cold snaps linger longer.

Get it wrong, and you’ll either watch seedlings freeze or rush crops that bolt in the heat. Washington’s climate is as varied as its landscapes, so timing isn’t just about the calendar—it’s about knowing your microclimate.

Whether you’re in Seattle’s rainy zone, Spokane’s dry interior, or the wine country hills, this guide breaks down the exact frost-date rules for your area and the best crops to plant each month.

You’ll learn how to stretch short seasons with simple tricks, avoid common pitfalls, and pick the right varieties for your USDA zone—so your garden thrives from spring to fall.

Washington State frost dates by region: key planting windows

Washington State’s varied climate creates distinct planting windows across regions. In the Pacific Northwest (Western WA), mild coastal air delays frost, while Eastern WA’s inland valleys experience earlier freezes. Understanding these frost dates helps you avoid killing tender seedlings or missing harvests.

Let’s break down the critical dates for Seattle, Portland, Spokane, and Wenatchee, along with ideal planting months for your garden.

Your USDA hardiness zone also matters—Western WA ranges from Zone 7b-9a, while Eastern WA spans Zone 5b-7b. These zones influence which cool-season crops (like kale and peas) thrive in early spring and which warm-season crops (like tomatoes and peppers) need to wait until after the last frost.

Let’s dive into the specifics for each region to help you plan your garden calendar.

Last spring frost and first fall frost dates are the backbone of your planting schedule. In Seattle and Portland, the last spring frost typically occurs between April 15 and May 1, while Spokane and Wenatchee see their last frost around May 15 to June 1. Conversely, fall frosts arrive earlier in Eastern WA—September 15 to October 1—compared to October 15 to November 1 in Western WA. These dates create a 120- to 150-day growing window for warm-season crops.

Here’s a quick comparison of frost dates and planting windows for Washington’s key regions, including ideal months for cool-season and warm-season crops:

For cool-season crops like lettuce, spinach, and peas, start seeds indoors 4-6 weeks before your last frost date. In Seattle or Portland, this means sowing in late February to early March, while Spokane gardeners should wait until mid-April.

These crops tolerate light frosts, so you can even plant them 2-3 weeks before the average last frost date for a head start.

Warm-season crops—such as tomatoes, peppers, and cucumbers—demand soil temperatures above 60°F and can’t handle frost. In Western WA, transplant seedlings after May 15, while Eastern WA’s shorter season means you should get them in the ground by late May to early June.

Use row covers or a cold frame to extend the season for heat-loving plants in cooler regions like Spokane.

Don’t overlook fall planting for crops like kale, carrots, and radishes. These thrive in cooler weather and can be sown 4-6 weeks before your first frost.

In Puget Sound, this window opens in late August to early September, while Spokane gardeners should aim for mid-July to early August. These late-season plantings often yield some of the sweetest harvests!

Pro tip: Use microclimate adjustments to fine-tune your planting. South-facing slopes warm up faster, while low-lying areas may frost earlier. If you’re unsure, check local Cooperative Extension Service reports or use a frost calendar app to track real-time data.

With these frost-date rules, you’ll be well on your way to a bountiful Washington garden.

Remember, succession planting is key for continuous harvests. For example, sow lettuce every 2 weeks from spring to early fall, and stagger bean plantings every 3 weeks for a steady supply. This strategy maximizes your garden’s potential, especially in regions with shorter growing seasons like Spokane or Wenatchee

Best crops to plant in each Washington season: month-by-month guide

Washington’s gardening season runs from early March to late October, but the best crops to plant depend on your microclimate. Coastal areas like Seattle and Bellingham enjoy milder winters, while inland zones like Spokane and Wenatchee face earlier frosts.

Below, I’ll break down the ideal planting windows for each season, tailored to Washington’s unique growing conditions.

For early spring, focus on cold-hardy crops like peas, spinach, and lettuce. These thrive in March-April when soil temperatures reach 40-50°F.

In late spring (May-June), warm-season crops like tomatoes, peppers, and cucumbers can go in once frost risk passes. Summer (July-August) is perfect for beans, zucchini, and basil, while fall (September-October) rewards you with kale, carrots, and radishes before winter sets in.

Pro Tip: Use row covers for early spring plants in colder regions (Zone 6-7) to protect against late frosts. In warmer inland areas (Zone 5), you can start warm-season crops 2-3 weeks earlier than coastal zones.

In Western Washington, where frost dates are later, you can extend your fall planting into early November for crops like spinach and arugula. Meanwhile, Eastern Washington gardeners should prioritize fast-maturing varieties (e.g., bush beans, cherry tomatoes) to beat the earlier frosts in October.

Always check your local frost dates—they vary by just 1-2 weeks between Seattle and Spokane!

For succession planting, sow bush beans and lettuce every 2 weeks from May to August. This ensures a continuous harvest and prevents wasted space. In cooler microclimates, like the San Juan Islands, opt for early-maturing varieties of tomatoes and peppers to avoid short seasons.

Don’t forget perennials like asparagus and rhubarb—they thrive when planted in early spring (March-April). Give them 2-3 years to establish before expecting a full harvest. With this month-by-month guide, you’ll avoid common mistakes like planting tomatoes too early or missing the fall harvest window for root crops.

Happy planting! Adjust based on your local microclimate, and soon you’ll be enjoying a bounty of homegrown produce all season long. 🌱