Get It Growing: How learning about climate zones helps local gardeners

Published 1:30 am Wednesday, June 24, 2026

Planning a garden involves numerous variables: location, sun, and water, to name a few. So the question is, “What plants will grow well in my area or climate?”

Climate can be described as an average of weather conditions for a specific region, averaged over a relatively long period of time. Climate is what the weather is statistically likely to be during any certain time of the year. Weather is what you think about when deciding how to dress for the day.

When researching plants, most descriptions refer to “zones.” There are the USDA Hardiness Zones and the AHS Heat Zones. Also, in the West, there is the “Sunset Western Garden Book” and its unique system of Climate Zones. So when you find a plant with USDA Hardiness Zone 8b, AHS Heat Zone 1, and Sunset Zone 4, what does that mean?

USDA Hardiness Zones

Revised in 2023, the U.S. Department of Agriculture defined zones based on the average annual minimum temperature using 10-degree increments; these zones are subdivided into separate 5-degree increments for better accuracy. Hardiness zones indicate a plant’s cold tolerance or its ability to “winter over,” with zone 1 indicating the coldest temperatures and zone 13 the most tropical.

Much of Sequim and Port Angeles falls within USDA Zone 8a-9a. However, and this is important, Zone 8b-9a is also the hardiness zone for Austin, Texas. Does that mean we can grow the same plants here that are grown in the southern United States? Not necessarily. We can grow plants with the same cold hardiness, but with too much or too little heat, they may not thrive.

AHS Heat Zones

The American Horticultural Society developed heat zones based on how many days per year the temperature typically goes above 86 degrees, known as “heat days.” It helps you determine if local summer temperatures are hot and long enough to support a plant, or if a location provides too much heat for the plant. Zone 1 indicates less than one heat day, and Zone 12 indicates over 200 heat days.

The Sequim and Port Angeles area is in AHS Heat Zone 2, with only 1-7 heat days. (Although it is still a guide, the AHS Heat Zone map was developed in 1997 and has never been updated. Some gardeners might suggest the heat zone in this area has approached Zone 3, with 8-14 heat days.)

Because the USDA Hardiness Zones are based on minimum temperature, while the AHS Heat Zones are based only on heat tolerance, neither of these systems considers other important climate factors such as growing season, humidity, or aridity, to name just a few.

Sunset Climate Zones

The “Sunset Western Garden Book” uses a wide range of factors in defining climate zones, including winter minimums, summer highs, elevation, rainfall, humidity, aridity, and growing season. As a result, it provides a more comprehensive view encompassing both the USDA and AHS data. All the plants described in Sunset include their range of zones. Most of the Olympic Peninsula is in Sunset Climate Zones 4 and 5, excepting the higher elevations.

Most nurseries and retail stores will have USDA Zones identified unless specifically noted otherwise. Fortunately, many local nurseries will also have a copy of the “Sunset Western Garden Book” available for reference. Take a moment to check what the Sunset Zone might tell you about the likelihood a plant will thrive in your area.

A great way to determine what landscape plants grow best in your immediate area is to go look around local neighborhoods and talk to fellow gardeners. A great opportunity to do that is coming up soon! The Clallam Master Gardeners are hosting the annual Petals to Pathways Garden Tour. This year, it will include properties in the Port Angeles area.

On Saturday, June 27, beautiful gardens will be open for the public to enjoy and learn from. Master Gardener docents will be on hand to help identify plants, answer questions, and offer tips on gardening in the PNW.

More information is available online at clallamcounty.mastergardenerfoundation.org.

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Susan Kalmar is a Clallam County Master Gardener.