2005 Prius moved from CA to WA state: Winterizing?

I would concentrate on the ice coolant and the inverter coolant.

Don't dump the whole ice coolant loop. Just dump the rad only then close the petcock and fill it back up. That way you do not invoke an airlock which on the g2 is a stone cold biatch to get air out. The remedial rad dump really helps. Do it once then do it again a month later that will really help.
Use Toyota LLC coolant.

I would replace the Inverter coolant make sure it has fresh LLC. Thats really easy to do and really easy to bleed.

Then I would start running thinner oil like synthetic 5-20 weight. Be aware your right in the range where many many people have reported oil loss from the engine eating oil so check the oil level once a week in the am before thew car has been started. Keep it at the full line.

And many peeps have bought engine block heaters they work great. Pretty easy to install.

And many many people block the rad with a piece of cardboard during the winter months.
If not the heater may not work well at sub zero temps.

Good Luck.

 

I believe that only a tiny fraction of Prius owners anywhere in the Puget Sound area bother with engine block heaters. This includes the San Juans. If you travel inland east of the Cascades in winter, then it would be more useful, but still not essential or very common.

Some sort of radiator block would certainly help with efficiency and cabin heat in winter, though is not essential. Prius owners everywhere most commonly use hollow foam pipe insulation stuffed into the grill. Cardboard in front of the radiator is very likely to get waterlogged in this wet climate, and is better in climates that stay below freezing for extended periods, which doesn't happen here. Sub-zero temperatures should be extremely rare, as in not every decade.

In addition to making sure the coolants are ready for PNW winters, make sure the window washer fluid is good too. Plain water, or even with just a little bit of alcohol, will freeze on the coldest days. I use fluid rated for -20F due to my inland trips, and it is readily available in the region. But anything rated to 0F is plenty good for the Islands, just don't use any 32F product.

Tires? This thread is dated, but should still have plenty of good info if you can wade through it:
Low Rolling Resistance replacement tires: Current List | PriusChat

 

You don't really need to do anything special. Not like you are in the Cascades or out on the Palouse.

Make sure you have good wiper fluid, as mentioned -- Rain-X or Prestone are good brands. I would not worry about special oil. I would NOT get a block heater.

Tires, I really, really like the General Altimax RT43. It is all-season, but has very decent snow and ice traction for an all-season. Consumer Reports rates it very highly.

The LRR tires are a bit of....well..... there is no official standard for them, and Ook, the caveman, could rate his round rock LRR, if he wanted to...The Altimax gets good miles and very reasonable in price.

You are in the San Juans. It's a temperate climate, although very wet. The Altimax does great in rain.

It's the only tire I use on all my cars now. https://www.tirerack.com/tires/tests/testDisplay.jsp?ttid=215

 

Hey, what can I say. You're right though.

Ours fritzed maybe a couple of months back, and I was going through withdrawal till I got the replacement installed. Engine sounds much happier on cold starts, and usually shuts off at the first traffic light, a couple of blocks away. More so if you turn the cabin heat/vent system temp lower, and/or right off.

 

Western Washington south of Mount Vernon may have 1 to 7 days of snow, usually 1.

Eastern Washington has winter, follow the advice you would for Minnesota.

The Bellingham area will have about 3 weeks of cold weather, I can see owning a block heater. Like Vancouver BC, which may be the best way to get one.

 

I had to wait about 3 weeks for it, they ordered it in. Still, likely easier to obtain here, yeah.