Historical weather data, all-time temperature records, and monthly climate averages for Clearlake, CA. Explore typical weather conditions by week for trip planning, and see how today compares to the historical record.
April 5 in Clearlake sits right in that transitional spring sweet spot — historically averaging a pleasant 67° high and 39° low across 59 years of records. There's only a 20% chance of rain today, though the date has seen its share of swings: a scorching 86° back in 1989, and a frost-threatening 29° in 2001.
Clearlake plays for keeps when the weather gets extreme. The mercury has soared as high as 114° (June 30, 1977) and crashed to a brutal 6° (December 22, 1990) — a 108-degree range that tells you this inland lake town is no stranger to intensity. A single January day in 1995 dumped 6.47 inches of rain, and a January 1974 snowstorm buried the area under 16 inches.
Summer is the undisputed star here, with late July averaging a sizzling 96° high — making Clearlake a warm-weather destination from June through September. Winter is mild by Northern California inland standards, with January highs hovering around 53°–55°, though rain picks up considerably, peaking the second week of January at over an inch on average. If you want heat, come in July; if you want to avoid getting wet, skip January.