Hardiness Zone Lookup

Find your USDA or RHS hardiness zone by minimum winter temperature and see which plants are suitable for your climate.

Zone Reference Table

How It Works

Plant hardiness zones are geographic areas defined to identify the best-suited plants for each region. They are determined by the average annual minimum winter temperature, which is the primary limiting factor for plant survival.

USDA Hardiness Zones

The United States Department of Agriculture (USDA) Plant Hardiness Zone Map divides North America into 13 zones (1–13), each split into “a” and “b” sub-zones representing 5°F (2.8°C) increments. Zone 1a is the coldest (−60°F / −51°C) and Zone 13b is the warmest (65–70°F / 18–21°C).

RHS Hardiness Ratings

The Royal Horticultural Society (RHS) uses a system of seven ratings (H1a–H7) common in the United Kingdom and Europe. H7 is the hardiest (surviving below −20°C / −4°F) and H1a is for heated greenhouse plants only.

How to Find Your Zone

• Check local records – Find the average annual minimum temperature for your area from weather services or gardening organizations
• Consider microclimates – Urban areas, south-facing walls, and sheltered spots may be warmer than the surrounding zone
• Factor in elevation – Higher altitudes are generally colder; adjust your zone accordingly
• Account for wind and moisture – Wind chill and wet soils can make effective temperatures colder than recorded air temperatures

Limitations

Hardiness zones only reflect minimum winter temperatures. They do not account for summer heat, humidity, rainfall, soil type, or day length—all of which affect plant growth. Use zones as a starting point, not the sole guide to plant selection.