California Climate Zone 16

Climate zone 16 covers the mountains, from the Siskiyous through the Sierra Nevada to the Southern California ranges — the coldest assignment in the state. The Energy Commission assigns 228 of California's ZIP codes to it, making it the 4th largest of the sixteen.

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Where zone 16 is

The Energy Commission assigns 228 ZIP codes to zone 16 — about 8.5 per cent of every ZIP code it lists, and the 4th largest of the sixteen. Places in it include Truckee, South Lake Tahoe, Big Bear Lake, Mammoth Lakes, Bishop, Tehachapi, Idyllwild and Mount Shasta.

The zone is scattered rather than contiguous, appearing wherever elevation or desert conditions occur — which is why neighbouring towns can be in different zones. The ZIP codes fall in the prefix ranges 910xx, 913xx, 917xx, 923xx, 924xx, 925xx, 932xx, 935xx, 936xx, 952xx, 953xx, 955xx, 956xx, 957xx, 959xx, 960xx, 961xx.

What drives compliance in zone 16

Heating dominates and it dominates decisively — this is the coldest assignment in the state. Insulation levels, air tightness and heating equipment efficiency drive the calculation, and requirements that look severe from a coastal perspective are ordinary here. Cooling is a minor consideration at most elevations in the zone.

Where zone 16 ends

Zone 16 is the most widely scattered of the sixteen, appearing in more ZIP prefix ranges than any other because it follows elevation rather than region. It turns up in the Siskiyous, the Sierra Nevada, the Tehachapis and the Southern California ranges, which is why a mountain address anywhere in the state has to be checked rather than assumed.

Boundaries follow conditions rather than administrative lines, so the assignment is resolved from the project ZIP code rather than inferred from the city on the drawings.

Cities we cover in zone 16

3 of our city guides cover places in this zone, and some of them cross a zone boundary inside the city.