Title 24 Reports in Trinity County

No city at all

Trinity is one of three California counties without a single incorporated city — Alpine and Mariposa are the others — according to the Department of Finance's 2026 population estimates. Weaverville, Hayfork, Lewiston and every other community here are unincorporated. Elsewhere a project's location decides between a city and the county as permitting authority; in Trinity that question has one answer, and it is the county.

Zone 16 in the Klamath Mountains

Zone 16 is usually described in Sierra terms — Truckee, South Lake Tahoe, Mammoth Lakes. Trinity's is a different range. Eleven of the county's 13 ZIP codes carry it, spread across the Trinity River towns — Weaverville, Lewiston, Douglas City, Junction City — up to Trinity Center and Coffee Creek below the Trinity Alps, and west to Hayfork and Hyampom.

For practical purposes, a Trinity County project is a zone 16 project unless its address proves otherwise. The mountain targets are the default here rather than the exception.

Downriver, the zone changes with the county

Highway 299 follows the Trinity River west out of the county. Burnt Ranch and Salyer, among the last Trinity communities on that road, are zone 16. Willow Creek, the next town downstream and across the line in Humboldt County, is zone 2. Over that short stretch a design changes county, zone and target all at once.

The southern tip

Zone 2 rests on two ZIP codes at the bottom of the county: 95552, which covers Ruth and Mad River and lies 93 per cent within Trinity, and 95595 to the south-west of it, wholly inside. Two ZIPs the county holds is enough to claim the zone, and counted this way Trinity is the only California county in which zone 2 and zone 16 meet. It is a mixed climate where summer cooling and winter heating both count, unlike the heating-first assignment that covers the rest of the county.

Every ZIP code by zone

Zones per the Energy Commission; county membership and community names per the 2020 Census.

• Climate zone 2 — 95552 (Ruth, Mad River); 95595
• Climate zone 16 — 95527 (Burnt Ranch, Trinity Village); 95563 (Salyer, Trinity Village); 96010; 96024 (Douglas City); 96041 (Hayfork, Post Mountain); 96046 (Hyampom); 96048 (Junction City); 96052 (Lewiston); 96091 (Trinity Center, Coffee Creek); 96093 (Weaverville); also 96076, split with a neighbouring county (below)

A ZIP code that crosses the county line

• 96076 — about 39% within Trinity County, the remainder in Tehama 34% and Shasta 28%

Trinity holds the largest share of 96076 but not a majority, and the ZIP's one Census community, Platina, is a Shasta County place. The zone is 16 wherever the address falls; the county line decides only which county permits the project.

Finding the zone for your own project

The zone is set by the project's location and confirmed from the ZIP code against the Energy Commission's published table — not from the county name and not from the nearest large town. Because Trinity County contains more than one zone, that check decides which set of numbers a report is written against.

Give us the project address and we determine the zone as part of preparing the report. It is the first thing established, because every insulation, glazing and equipment figure downstream depends on it.

Climate zones in Trinity County

Trinity County contains California climate zones 2 and 16. The zone drives the insulation, glazing and equipment performance a report has to demonstrate, and it is confirmed from the project ZIP code against the Energy Commission's published table.