Hetch Hetchy, CA Climate

Climate Insight: Hetch Hetchy, CA

Based on station USC00043939 feeding NOAA's 1991–2020 climate normals, Hetch Hetchy, California averages 55°F a year, ranging from a mean daily high of 66°F to a mean daily low of 44°F. July is typically the warmest month of the year, while December is the coldest. Because these figures are thirty-year averages rather than any single year's readings, they describe the typical month, not a forecast for it.

Hetch Hetchy averages 36.9 inches of precipitation a year, with 51.4 inches typically falling as snow, and that matters as much to daily life here as temperature does. The frost-free season averages 210 days, which directly shapes the planting calendar and growing potential for the area, with the last spring freeze near April 16 and the first fall freeze near November 12. As for energy demand, 4,377 heating degree days and 729 cooling degree days tell the story of how often furnaces and air conditioners run during a normal year.

On PlainClimate's composite comfort index, Hetch Hetchy scores 58/100 (Moderate), a blended measure that weighs temperature mildness, precipitation moderation, and extreme-weather frequency against one another. The monthly tables above turn that into a planning tool: expect the mildest highs and lows in the shoulder seasons, July-driven heat at the peak of summer, and December-driven cold at the depth of winter. Every number here is a thirty-year average, not a forecast, so any given year can and does run warmer, cooler, wetter, or drier than the normal.