Climate Sonoma County, California

sonoma county s dry creek valley

sonoma county, case coastal counties in california, has great degree of climatic variation , numerous, different, microclimates. key determining factors local climate proximity ocean, elevation, , presence , elevation of hills or mountains east , west. in large part due fact that, throughout california, prevailing weather systems , wind come pacific ocean, blowing in west , southwest places closer ocean , on windward side of higher elevations tend receive more rain autumn through spring , more summer wind , fog. partly result of presence of high , low pressures in inland california, persistent high summer temperatures in central valley, in particular, leading low pressures, drawing in moist air pacific, cooling damp cool breezes , fog on cold coastal water. places further inland , particularly in lee of significant elevations tend receive less rain , less, in cases no, fog in summer.

the coast typically cool , moist throughout summer, foggy, fog blowing in during late afternoon , evening until clears in later morning sunny, before repeating. coastal summer highs typically in mid high 60s, warming low 70s further ocean.

certain inland areas, including petaluma area , santa rosa plain, prone normal fog pattern in general. however, tend receive fog later in evening, fog tends more short-lived, , mid-day temperatures higher on coast, typically in low 80s f. particularly true petaluma, cotati , rohnert park, and, less so, santa rosa, windsor, , sebastopol. in large part results lower elevations , prominent petaluma gap in hills between ocean west , petaluma valley , santa rosa plain east.

areas north of santa rosa , windsor, larger elevations west , further fog path, tend receive less fog , less summer marine influence. healdsburg north of windsor less foggy , warmer, summer highs typically in higher 80s 90 °f (32 °c). sonoma , sonoma valley, east of petaluma, similar, highs typically in high 70s f 80 °f (27 °c). in part due presence of sonoma mountains between petaluma , sonoma. cloverdale far north out of santa rosa plain, hotter other city in county, rare evening-morning fog , highs in 90s, reaching 100 °f (38 °c) more other cities. notably, however, temperature differences among different areas of county greatest highs during mid-day, diurnal lows more throughout entire county. lows closely tied evening-morning cooling marine influence, in addition elevation, bringing cool temperatures of region.

these weather patterns contribute high diurnal temperature fluctuations in of county. in summer, daily lows , highs typically 30-40 °f apart in land, highs petaluma, cotati, rohnert park, santa rosa, windsor, , sebastopol typically being in low 80s f , lows @ or near 50 °f (10 °c). healdsburg , sonoma, similar lows, have greater diurnal fluctuations due warmer highs. on other hand, coast, strong marine influence, tends have low diurnal temperature fluctuation, summer highs cooler inland towns, typically 65-75 °f, yet lows in high 40s low 50s f, comparable inland towns.

these microclimates evident during rainy seasons well, great variation in amount of rainfall throughout county. generally, of sonoma county receives fair amount of rain, of county receiving between 25 in (640 mm), comparable areas such sonoma , petaluma, , 30 in (760 mm) normal santa rosa. however, areas, particularly in north-west portion of county around russian river, receive more rainfall. guerneville area, example, typically receives 50 in (1,300 mm) of rain year, annual rain going high 70 in (1,800 mm). nearby cazadero typically receives 72 in (1,800 mm) of rain year, many times has reached on 100 in (2,500 mm) year, , on 120 in (3,000 mm) of rain year. cazadero region second wettest place in california after gasquet.

snow exceedingly rare in sonoma county except in higher elevations on , around mayacamas mountains, particularly mount saint helena, , cobb mountain peak across line of lake county.