Guide · November to March
The wet season on the north coast
Eureka averages 40.4 inches of rain a year, and 77 percent of it falls from November through March (NOAA, 1991-2020 normals). Here is the rain month by month, what Humboldt and Trinity County's rules say about grading, and how hard the climate is on outdoor wood.
November to March
Sources
- NOAA National Centers for Environmental Information, 1991-2020 normals: Eureka (Woodley Island)
- Humboldt County Code §331-14 (grading, excavation, erosion and sediment control)
- Humboldt County: Residential (Standard) construction documents
- Trinity County: Grading Permit Information
- USDA Forest Products Laboratory: Decay Hazard (Scheffer) Index Values, 1971-2000 (FPL-GTR-179)
| Month | Inches |
|---|---|
| January | 6.67 |
| February | 5.64 |
| March | 5.75 |
| April | 3.64 |
| May | 1.66 |
| June | 0.70 |
| July | 0.18 |
| August | 0.18 |
| September | 0.68 |
| October | 2.31 |
| November | 4.89 |
| December | 8.10 |
The numbers
Eureka averages 40.4 inches of rain a year, and 77 percent of it falls from November through March (NOAA, 1991-2020 normals).
Source: NOAA National Centers for Environmental Information, 1991-2020 normals: Eureka (Woodley Island)
Humboldt County's winter period for grading
The county's grading ordinance treats October 15 through April 15 as the winter period.
Under Humboldt County Code §331-14, a site-specific erosion and sediment control plan has to be submitted with any development application involving grading that has any one of these characteristics: it covers one acre or more; it is on a slope of 15 percent or steeper; it is in an area of moderate or high geologic instability; it is within a Streamside Management Area or other wet area; it is within a floodplain; it is for a driveway or road longer than 300 feet; or it is planned for the winter period, October 15 to April 15.
The Chief Building Official may also require a plan, prepared by a qualified professional at the owner's expense, at any time during design or construction.
On projects that need a building, grading or development permit, bare ground has to be seeded and mulched before October 15, unless the project's conditions say otherwise.
Source: Humboldt County Code §331-14 (grading, excavation, erosion and sediment control)
Grading plans
For a house in unincorporated Humboldt County, the county asks for a grading plan when the grading is 50 cubic yards or more (not counting the foundation excavation), or when the job triggers the county grading ordinance in any other way.
Trinity County grading permits are applied for through the county Planning Department, on its Director's Use Permit application, and the review itself is done by the county Department of Transportation.
Sources: Humboldt County: Residential (Standard) construction documents; Trinity County: Grading Permit Information
Outdoor wood
The USDA Forest Products Laboratory rates how hard a place's climate is on wood left outdoors above the ground with a decay hazard index: the higher the number, the greater the hazard.
Its table of values for 1971 to 2000 lists Eureka at 44.5.
Source: USDA Forest Products Laboratory: Decay Hazard (Scheffer) Index Values, 1971-2000 (FPL-GTR-179)
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