Marin Master Gardeners
University of California
Marin Master Gardeners

Climate Zones

What is my climate zone?

Most gardening books, catalogs, and seed packets refer to plant hardiness zones, climate zones, or growing zones. Temperature hardiness climate zones are based on normally expected high and low temperatures and serve as guides to help you know which plants will grow where you live.

  • The USDA plant hardiness map divides North America into 11 hardiness zones. Zone 1 is the coldest; zone 11 is the warmest. When you order plants from catalogs or read general garden books, you need to know your USDA zone in order to be able to interpret references correctly.
  • The American Horticultural Society has also issued a Plant Heat-Zone Map.  
  • The Sunset zone maps, considered the standard gardening references in the West, are more precise than the USDA's, since they factor in not only winter minimum temperatures, but also summer highs, lengths of growing seasons, humidity, and rainfall patterns.
  • Marin County is situated in SUNSET Zones 15, 16, and 17. The table below lists the cities and towns in Marin County and the associated SUNSET climate zones:

Sunset Garden Zone

Climate Conditions

Marin Cities and Towns Located in this Zone

Comments

15

COASTAL CLIMATE Some winter frosts, warmer summers with afternoon winds

Fairfax, inland areas of San Rafael, Terra Linda, Lucas Valley, Novato, Mill Valley, Inverness, Point Reyes Station, Mill Valley hilltops

Lowland valley areas and hilltops will receive the most frost. Average low temperatures 28 – 21 degrees F.

16

NORTH COAST THERMAL BELT Has more heat than Zone 17 and warmer winters than Zone 15. Summer afternoon winds.

San Anselmo, Lagunitas, Mill Valley, Ross, Kentfield, Larkspur

Lowland valley areas and hilltops will experience colder winters. Average low temperatures 32 – 19 degrees F.

17

MARINE EFFECTS Mild, wet winters and cool summers with frequent fog and wind.

Sausalito, Tiburon, Belvedere, Tomales, Bolinas, Corte Madera, eastern San Rafael and Novato

Hilltops with southwest facing slopes experience hotter summers. Average low temperature 36 – 23 degrees F.

The zones are only a guide and a good starting point, but you still need to determine for yourself what will and won't work in your garden.

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