Some very cold air is descending on the Bay Area this week ahead of another storm system, and all signs point to Tuesday morning likely being the chilliest that San Francisco has seen in four years.

The mercury hasn't hit 39 degrees in the city since January 6, 2017, according to the National Weather Service's Bay Area bureau, but it may do so again tomorrow morning and hit freezing temperatures of 32 or below across the North Bay at the same time. For much of the country, this kind of winter chill is child's play, and 39 is practically shorts weather in Chicago. But here in the Bay Area, that is FREEZING and you will likely see a lot of social media posts to that effect tomorrow.

The high on Tuesday will still be a usual, temperate-SF 49 or 50 degrees. But you might see more low lows on more mornings this week, so perhaps crank up the heat or pull out an extra blanket to throw on the bed.

Meanwhile, the rain continues, and it was especially heavy in the South Bay Monday morning. Expect more rain through Wednesday in SF, with Thursday bringing the first break in what feels like forever. Friday and the New Year's weekend will be sunny and chill — and the mornings will be especially cold, still, with the Weather Channel predicting a low of 38 degrees on Saturday morning.

And Tahoe has seen incredible amounts of snow in the last week, and it's still not letting up. A 70-mile stretch of I-80 through the Sierra was shut down to traffic for most of the weekend and into today, and other roads were closed as well due to white-out conditions.

As Tahoe ski expert Kevin "Coop" Cooper tells KTVU, "This is probably the most snow that I’ve seen in a single system in quite some time, we’re talking over a decade." There are reports of 10-foot snow drifts and piles in driveways, and it's already being called "The Blizzard of '21."

And as Cooper writes on Twitter today, "With the roads closed, neighborhoods unplowed and another day of wind, and snow fall ahead, its time to hunker down, shovel out, and get yourself ready to kick off 2022 with our snowpack well over 190% for the month of Dec."

Photo: Osman Rana

You'd better bundle up even more than usual if you're forgoing a New Year's Eve in San Francisco for an event in the South, East, or North Bay — forecasters say that temperatures in those areas will plummet as low as the 20s on the last night of this cursed, shitty year.

According to the Chron, temperatures in the Bay Area are expected to start to drop Friday. San Francisco can expect weather in the mid-40s on New Year’s Eve and New Year’s Day, which isn't too bad. However, temps in the East Bay and South Bay will drop to the 30s "and Sonoma and Marin counties could see the 20s," they report.

According to the Ex, we can blame our neighbors to the north for the drop, as it's "a flow of air from Canada moves south into Northern California" that will send the mercury plummeting. Monday and Tuesday will also be chilly in SF, they report, as "daily highs may not reach 50 degrees."

Related: Seven New Year's Eve Parties For Locals

Though the worst of the current Bay Area freeze might be behind us, that doesn't mean it's time to pull out the shorts and flip-flops. Forecasters say residents should expect today's cold weather to continue for the rest of the year... and beyond.

According to the National Weather Service, the current weather pattern hit its nadir Sunday morning, with Pleasanton at 22 degrees, Menlo Park at 25, and Novato at 26. Golden Gate Park was a relatively balmy 32 degrees, which resulted in cars on the west side being blanketed in frost even as late as 8 a.m.

"It's like, am on the East Coast?" asked Kathy, a SF native and my across-the-street neighbor in the Outer Sunset, as she tried to scrape the ice off her RAV-4's windshield with a credit card.

"Do you have an ice scraper?" she asked me. "I don't! I don't know anyone who does...can I just pour hot water on this?" (Don't worry, guys, I talked her out of that one, after a muttered "Jesus, California.")

But while Kathy's windshield will likely remain clear for the next few days, it'll still be cold, cold, cold, Drew Peterson, meteorologist for the National Weather Service, told the Chron.

“It’s going to be several days of dry, cold weather ahead,” Peterson said.

“Sunday was probably the last day of freezing temperatures so widespread, but we’re in the middle of winter now, and it’s expected to be cold.”

The reason for the low temperatures, Peterson says, is the lack of wind.

"Usually the Bay Area gets protected because it’s near the water, but that didn’t happen because there wasn’t any wind to help...Without those winds, the coldest air settles.”

Forecasters aren't sure when the current weather will change, as a weather pattern known as a Rex Block (also, my porn name) will keep the area dry for the foreseeable future.

Atmospheric blocking, meterologist Jeff Haby says via weatherprediction.com, "leads to a stagnation of weather patterns...for several days to even weeks." In the case of a Rex Block two adjacent high and low pressure systems causes "the airflow to move from high latitudes to low latitudes with little comparable west-east movement of the air," leading to little change in weather for us on the ground for days at a time.

So keep that coat, hat, and pair of gloves at the ready. You're gonna need them for a good, solid while.

If you woke up this morning wondering why you had no feeling in your fingers, you're not alone. A frost advisory was declared for parts of the Bay Area — with temperatures reported as low as the 30's — in what is turning out to be the coldest morning in months.

ABC 7 notes that black ice was possible around Petaluma and Santa Rosa earlier in the day, and reminds us that when the temperature gets this low people should cover sensitive plants and make extra efforts to keep pets warm.

The frost advisory was in effect throughout the night until 9:00 a.m. this morning.

Thankfully, things are set to warm a bit this week, with the National Weather Service predicting a high of 66 degrees for both Friday and Saturday in San Francisco. But get your park day in quickly, as rain is expected for Sunday.

Warm Saturday news aside, this morning's chill caught at least one Bay Area resident by surprise.

Today you can expect to be blasted with some really cold (for us) Canadian air, if you haven't been already. Despite sunny, dry conditions, a cold weather system is blowing down on the Bay Area from the north, as KRON 4 and others are reporting, making for some truly chilly, wintry weather as we head toward New Year's Eve. Also, it's going to get really, unpleasantly windy.

Overnight lows in San Francisco are going to dip below 40 degrees — something that only ever happens about once a year, for you new kids — and afternoon temperatures are going to top out in the low 50s. But it will feel colder than that, and you will need to pull out some of those special, wooly layers that are usually too warm for SF. And you'll probably want gloves, even though everyone from everywhere east of the Rockies will mock us for complaining about such temperatures. This is, in point of fact, balmy spring weather for Minnesota.

As CBS 5 reports, there's a high-wind advisory in place for all coastal and valley areas with "sustained north to northeast winds of 20 to 30 mph for the area [and] gusts to 60 mph in the highest elevations."

This means tonight, and on New Year's Eve, it's going to be time to hunker down at home, or at a fireplace bar, with hot toddies and mulled wine and such.

And take note that your iPhone/Weather Channel forecast for today looks like this, utilizing a blowy wind icon I'm not sure I've seen before:

It is freezing, people. Never before and never again shall we feel such glacial temperatures. Except for tomorrow, which is expected to get even colder. If you can imagine such a plight. Can you imagine such a plight? We cannot. Because the electrical impulses and chemical signals carrying messages to our brain have turned into tiny icicles.

Here in San Francisco we felt temperatures in the low 40s. Staggering. The Chronicle points out that other areas reached even lower numbers, which seems impossible but there you have it. "Santa Rosa hit 27 degrees, as did Woodside. Walnut Creek dipped to 30." This is bedlam.

Be sure to whine about today's chilly weather to your nearest East Coast transplant. It bugs the shit out of them and thus is quite hilarious.

Oh, and wear a scarf. A nice one, preferably.

The arctic chill, which should start to subside once the rain comes later tonight, broke weather records across the Bay Area. Early this morning, "San Rafael had a low of 28 degrees, tying the city's previous record for the date set in 1972," reports CBS 5. "The North Bay had some of the lowest recorded temperatures in general ... with many areas reaching the low-20s."

Moffett Field tied a record low of 31 degrees today, beating a record set in 1994.

Santa Cruz hit a record low of 27 degrees for the date.

Salinas recorded a low of 29 degrees, "breaking its previous record of 30 degrees set in 1980."

CHP reports that "black ice caused several crashes on the U.S. Highway 101 and Interstate 280 connector before dawn Tuesday." Brisk-related traffic advisories were issued along I-280, Hwy 101, and state Highway 17. And finally, Flights at SFO and Oakland were delayed for more than an hour in order to de-ice aircrafts.

At around 4 a.m. this morning, moments after our dry skin-inducing heater turned off, we checked our iPhone's weather app and noticed a jarring number: 31 degrees.

What?

Yes, it was freezing last night here in San Francisco. Records low temperatures were recorded in the North Bay too, with San Rafael registering at 32 degrees as of 9:30 a.m.

CoCo Times says that "[c]ommuters are braving sub-freezing temperatures throughout the Bay Area that have prompted weather officials to issue freeze warning along the region's roadways."

For tomorrow, inland areas can expect "temperatures of 28 degrees or lower" and more rain is anticipated for Wednesday evening, "with more rain into the end of the week," SF Chron reports.

Anyway, yeah, it's cold. We know this shock this annoying most of you California transplant readers. We'll try to stifle our amazement at this recent arctic chill blanketing the Bay Area. But still, wow; it sure is brisk.

It looks like it snowed right here in San Francisco yesterday and last night. Can you believe it? According to reports the snow was white, fluffy, and cold to the touch.

Also, the National Weather Service has issued a snow advisory for any and all Bay Area elevations above 2,000 feet. Bits of snow have hit the ground all the way from Sonoma to the Santa Cruz Mountains.

Bundle up, folks. The entire Bay Area is expected to freeze over starting tomorrow. In addition to the anticipated rainfall and ninth-circle-of-hell cold weather, the weather service suggests that that snow levels could drop "as low as 2,000 feet on Saturday and Sunday and possibly as low as 1,500 feet by Monday." That is to say, areas in the Santa Cruz Mountains and the North Bay hills could be affected by snowfall, so anticipate road closures. Check back at Weather Underground throughout the weekend for up to the second forecasts. (Temperatures could dip as low as the high 30s. God help us all.)

No!

Due to the awesome unseasonably cold weather the Bay Area has experienced over the last few months, an estimated 10 to 15 percent of Sonoma County's $400 million vino crop has succumbed to frost damage according to an NBC 4. (An aside: love NBC 4! Most entertaining newscast in the history of the world, ever!)

The crisp and energizing weather has also affected vineyards in Mendocino and Lake counties, "where damage to the crop is expected to be about 20 percent." According to a Napa Valley vintner spokesperson, NV has experience little to no crop damage "because most growers have adequate frost protection." (Oh, fighting words. Angela Channing would have you killed for such a verbal swipe.)

Since we're reportedly under the breeziness of "hurricane"-like winds, can we name the storm? If so, can we name it "Mary-Kate," then? Great.

In addition to shutting down the Richmond Bridge, closing the ferries, screwing with the chi of (the) 101, and getting our demin damp, Mary-Kate has so far also caused over 518,000 residents in the Bay Area to lose power. (Including the Whole Foods on Fourth Street. Bah.) A PG&E spokesperson said that some of the lost power could take as long as tomorrow morning to restore.

Damn you, Mary-Kate.

Update: In case you don't know, or have since succumb to a fatal infection while waiting for a bus, Muni has some serious service disruptions today. A (truncated) list of Muni's weather-related SNAFUs after the jump.

(Before we begin, we should point out that all of this rain is very good for us. That said, it is our God-given right as Californians to go clinically insane over the slightest change in weather patterns. So: %@#%^W$&^&!)

SFist Deborah snapped up the picture above this morning from high atop San Francisco's Glen Park/Sunnyside neighborhood. She sent it to SFist HQ with a message along the lines of, "Hey, look at this dead Xmas tree. Ha Ha." Cute, huh?

the jump, check out the "after" shot to see what the storm did only a few minutes later.