ZONE 4: Mid to High Elevations of the Mid Klamath, areas with Cold Winters
As one gains elevation in the Mid Klamath the growing season shortens due to late Spring and early Fall frost, and more snow in the winter. One of the West’s most narrow, linear climates, Zone 4 runs from high in the coastal mountains of Northern California to southeastern Alaska, losing elevation as it moves north. It gets considerable influence from the Pacific Ocean, but also from higher elevation. Extending the season with a cold frame, greenhouse and row covers is key to a productive garden.
Average winter lows in Zone 4 range from 34°F (1°C) down to 28°F (–2°C),with extreme lows averaging 8 to 0°F (–13 to –18°C). The growing season is 150 to 200 days long, but because Zone 4 summers are temperate (highs average from the low 60s to the 70s), plants take more time to develop. If you’re growing vegetables, for example, add at least 50 percent to the days-to-harvest figure listed on the seed package, or start your garden from transplants.