Sacramento weather in December

Someone asked what time of day the fog rolls in during late December and got corrected, repeatedly: "fog is more of a summer phenomenon. It is more about clouds and rain in winter." One poster explains the mechanism — "fog is a function of the cold air over the Pacific being drawn to hot inland temps; in winter inland temps aren't hot, and ergo no typical fog" — so if December fog appears at all, it "usually doesn't roll in until around or after dark." What replaces it is storms, and the honest answer to any timing question in December is "it depends entirely on the storms, not time of day." Regulars suggest a Golden Gate webcam over a forecast. The other thing to plan for: "dark is pretty early, around 5pm." Our record: 12 rain days, 126mm, 9.6 daylight hours.

Regulars name this among the better times to be here specifically because Capitol Park's 40 acres burst into blossom while the city still avoids both the summer crowds and the valley's thick winter fog. Our row backs that mild, still-rainy read, 19.4C over 7.9C nights feeling 6C, with 78.6mm of rain across 8.5 days and humidity at 70 percent. Regulars are specific this window through May suits walking Old Sacramento's historic waterfront and the farm-to-table restaurant scene without needing to dodge either extreme, and day-trip suggestions from regulars lean toward the nearby wine country or the American River Trail once a dry stretch lines up. A light rain jacket over layers is the standard packing answer for a changeable spring day. The record: 9.2 hours of sun, a 14.4 kph wind and AQI 39.

Regulars are matter-of-fact about the heat here, noting temperatures can hit the mid-30s Celsius at the hottest point of the day, and that everything - restaurants, shops, cars - is air conditioned as standard for exactly that reason, with one long-time resident calling it not especially remarkable even into July. Our row backs the dry heat directly, 33.5C reading as a real 34C, over 15.6C nights, with rain almost entirely absent, 1.5mm across half a day, and humidity down to a desert-dry 43 percent. The evening cools noticeably more than the daytime heat might suggest, dropping to the high teens Celsius after dark. The record: 13.6 hours of sun, a 15.7 kph wind and AQI 42.

The local variable has a name here: the delta breeze, cool air off the bay that gets through the one break in the coastal mountains and reaches the valley, usually in the evening. Regulars say it can take a hundred-degree afternoon down to the low nineties, and that the day normally drops about thirty degrees between mid-afternoon and midnight - which is our row exactly, 32.4C by day against 15.5C at night, a seventeen-degree Celsius fall. That is why people here plan the outdoors for after six. September and October are their recommended window: the heat is easing, the roads are open and the visitors have gone. Rain has not started, 3mm across 0.7 days at 48 percent humidity. The record: 11.4 hours of sun and AQI 39.

May is the month Sacramento regulars name: the winter fog has gone and the valley heat has not properly arrived, our row giving 28.4C days at 49 percent humidity with 1.9 precipitation days. The local feature worth knowing is the delta breeze - cool ocean air that reaches the Central Valley through the gap in the coastal mountains at San Francisco Bay. It usually arrives in the evening and drops the temperature about 30 degrees Fahrenheit between mid-afternoon and midnight, which is the difference between a 95F noon and a comfortable 80F evening, and is why outdoor evenings here work at all in the warm half of the year. Our row's 12.7C night under that 28.4C day is the same fact. The record: 15.1mm of rain, 12.7 hours of sun and AQI 39.