Okay, even in San Diego, I do have some winter prep:

Get my jacket out of my GHB and start actually wearing it.

Light the pilot on the heater.

Take down the smoke/CO alarm and run the heater for a few minutes to burn off the dust.

While it's down, check the batteries in the smoke/CO alarm.

Take the light blanket off the bed and put on the heavy one.

Winter in Vancouver means putting the good road bike on the trainer in the garage and getting out the other bike with fenders.

(And this year preparing to get mad about the extra traffic for the olympics.)

For the car - I leave snow tires on the car year round, so I just throw in a snow brush, and fill the washer fluid with my special no-freeze mix. If I have any water bottles in the trunk, I remove them.

For the garage - If I'm smart, I winterize the lawn mowers. Usually I'm not smart.

For the house - Check the fuel supply, have the furnace checked if it's been a while, bring in any hoses, possibly prune trees.

I have a backup kerosene heater, and I should do the annual check up on it. I should have my trees checked, too. Have the name of a guy to call, just haven't made the call yet.

We've had a little taste of winter here, with snow lying on the ground as low as 1000 feet. Temperatures are now hoovering around 30-40. Not really that much of preparations as most of our stuff is ready to use anyway, and the really important stuff is mostly done.

Get all the winter clothing for us and the kids (done).

Snow tires on the car (done).

Shovel + ice scraper in the car (done).

Lubricate cars door locks and rubber gaskets. (I use anti-freeze coolant solution all year, better rust protection and no reason not too, so that's not an issue)

Stuff the canoe indoors.

Snow tires on my bike.

Move the lawn one final time before it frosts. (If it gets dry enough during the day, that is... little "drying power" left in the sun at this time of year.)

Clean and prep the skis.

Buy a new scraper. Check the fluid levels in the vehicle. Think about snow tires.

And on the night of the first snow fall being forcasted, bangers and mash.

You can wait that long?

Snow tires have been mentioned by others in this thread and by myself in another thread.
The odd thing is I have been using all season radials for years. Other than the fact you need to replace them when they get worn enough that they don't grab as well instead of when the tread is down to the limit they have been fine.

Raining now.

Getting into mid 40s at night low / mid 50s during day.

Then 70 by friday!

There is a huge difference between snow tires and all-season tires. I think the term is "does not excel at ANY conditions" is appropriate for all-season tires.... Snow tires excel at snow and ice and has crappy performance on wet or dry asphalt, particular when the temperature is above 50F. (Not to mention you wear them out them pretty fast in high temperatures). If you try it, you'll be amazed of the performance gap between "all season" and a dedicated snow/ice tire.

That being said, those all-season tires may be appropriate for you and your climate. You can rotate tires for the season, but you can't rotate tires each time the weather changes...

Reducing speed to match your grip is the key, plus a little bit of slippery road training does not hurt either .... Another tip: At the start of the season I always test my grip when I'm uncertain of how much grip I really have. I brake hard at a safe location and speed to see what happens. (If your car hasn't ABS you should be ready to release that brake pedal PDQ). I will also seek out areas where I can play and practice - just provoking a little slip so I get the feeling of it, and how to control and correct it. Rundabouts are great for this purpose (when empty!)...

I used to believe all-season tires were useless in winter, and probably most brands are, but some aren't bad. I still don't like them, and don't believe even the best all seasons are a match for decent snow tires in snow, but the good ones do work in snow. That all seasons don't work well at all with moderate tread wear is also true.

As far as using snow tires on dry or wet pavement, it depends on the tire. I run Goodyear Ultra Grips, which are H rated and work great in wet weather and just fine dry. They do wear faster than the "million mile" summer tires that some people like, but they also stick far better in the corners than those things do, too. In a hot climate I'm sure snow tires in summer would be a poor choice, but where it barely gets above 80f in the summer, no problem. The biggest differences compared to all seasons in summer is that they're noisy, but I don't mind that, and also that these particular tires, on my car, are very resistant to hydroplaning.

Driving experience is certainly a big part of snow driving, but even a great driver can't make a car go up a steep snowy grade with bad tires.

As they say - YMMV.