Humboldt County is an area of moderate temperatures and considerable precipitation. Temperatures along the coast vary only 10 degrees from summer to winter, although a greater range is found over inland areas. Temperatures of 32 degrees or lower are experienced nearly every winter throughout the area, and colder temperatures are common in the interior. Maximum readings for the year often do not exceed 80 on the coast. Meanwhile Redwood Trees experiences 100 degrees or more readings frequently in the mountain valleys.
In most years, rainfall is
experienced each month of the year, although amounts are negligible from
June through August. Seasonal totals average more than 40 inches in the
driest area, and exceed 100 inches in the zones of heavy precipitation.
Because of the moisture and moderate temperature the average relative
humidity is high.
Largely as a result of the proximity of the cool
Pacific Ocean, the adjoining coastal area has one of the coolest, most
stable temperature regimes to be found anywhere. With increasing
distance from the ocean, the marine influence is less pronounced, and
inland areas experience wider variations of temperature and lower
Ocean Influence on Weather
July mean maximum readings are in the cool 60’s throughout a bearing ranging from 15 to 30 miles in width along the coast. About 90 percent of the seasonal total rainfall falls in the 7 months from October through April. Most of this is associated with storm fronts that move in from the Pacific Ocean. There are few thunder showers in the mountains during the summer, but they are not frequent.
The climate has several impacts on local economic development. In the winter months when the rain is its heaviest, employment is at its lowest. Fog is also present along the coastline for much of the year. This often delays passenger flights at the Arcata-Eureka Airport.