When to Plant a Garden in Washington State: Frost-Free Dates by County and Plant Type

Planting a garden in Washington State depends on when your last spring frost arrives — and that date can swing wildly from March in Spokane to May in the San Juans, depending on where you live.

Washington State’s diverse climate—from the rainy Pacific Northwest to the arid Columbia Basin—means your planting schedule depends on where you live and what you grow. Get the exact frost-free dates by county and plant type to maximize your garden’s success this year.

Cool-season crops like peas and lettuce can often go in as early as February in Eastern WA, while tomatoes and peppers need to wait until after May 15th in Western WA. The difference between a thriving harvest and a frost-nipped failure often comes down to timing.

Below, I break down the best planting windows for your region, how to prep soil for Washington’s varied conditions, and the one trick that extends your growing season by 3-4 weeks—no matter where you garden.

Washington State frost-free dates by county: when to start planting

Washington State's frost-free dates vary dramatically across its diverse climates, from the coastal rainforests of the Puget Sound to the hot, dry valleys of the Columbia Basin. These dates determine when you can safely plant warm-season crops like tomatoes and peppers without risking frost damage.

Let's break down the last spring frost and first fall frost dates by region and county.

Understanding your USDA hardiness zone is crucial because it helps you select plants that thrive in your area's average minimum temperatures. Most of Western Washington falls within zones 7b-9a, while Eastern Washington ranges from 5b-7a.

These zones influence when you can plant both cool-season crops (like lettuce and peas) and warm-season crops (like cucumbers and squash).

For example, King County in the Puget Sound region typically has its last spring frost around March 15, while Spokane County in Eastern Washington often sees its last frost around May 1.

These differences mean gardeners in Spokane can start planting much later than those in Seattle. Always check local weather forecasts for the most accurate timing, as frost dates can shift yearly.

Below is a county-by-county breakdown of Washington State's frost-free dates, including key regions like the Puget Sound, Eastern Washington, and the Columbia Basin. This table will help you plan your planting schedule with confidence, ensuring your garden thrives year after year.

If you're in the Puget Sound

Best planting times for vegetables, flowers, and herbs in WA

Washington State’s varied climate means your planting schedule should align with seasonal shifts and microclimates. Urban Seattle gardens thrive in cooler, wetter conditions, while Eastern WA’s dry heat demands water-wise timing.

I’ll break down the best months for cool-season crops, warm-season favorites, and perennial plants to help you time your garden perfectly.

For cool-season vegetables like kale and peas, aim for early spring or late summer plantings. These hardy plants tolerate light frosts and even thrive in cooler temperatures.

Meanwhile, warm-season crops such as tomatoes and peppers need to wait until after the last frost—typically mid-May to June in most of WA. Perennials like strawberries and lavender have different timing needs, often benefiting from fall planting for established root growth.

Here’s a quick guide to help you plan your garden by season:

Adjust your timing based on urban vs. rural locations. Cities like Seattle and Spokane have later frost dates than rural areas, while Eastern WA’s Yakima Valley can plant warm-season crops 2-3 weeks earlier due to warmer soil.

Always check your local frost dates—they’re your garden’s best friend for success.

For herbs like basil and cilantro, timing is critical. Basil needs warm soil (60°F+) and won’t survive frost, while cilantro thrives in cooler spring temperatures. Plant basil in late May or June and cilantro in early spring or fall for best results.

Similarly, lavender and rosemary prefer fall planting to establish roots before winter.

Pro tip: Use row covers or cold frames to extend your growing season for cool-season crops in late fall or early spring. This trick works wonders in Western WA’s rainy climate, where frost can linger longer. With the right timing, you’ll enjoy a bountiful harvest all season long! 🌿