The region that's on fire is like an hour's drive away from Berkeley. Unless you anticipate camping on the freeway, I don't see how 48 hours of water is really an essential. The supply chain isn't in much danger except in the very local area you would be evacuating.
In Australia we've had bush fires hit remote communities who've then been short on all sorts of supplies for days at a time. Not to mention in having an extra days worth of 'stuff' you'll have enough to go around.
The idea is you want to make it harder for the fire to get a foothold on your roof - that's a death sentence for the house in most cases.
Is it ideal? No. Is it a pain in the ass to remove? Yeah, kinda.
But it expands and hardens to a watertight closed-cell foam plug, which is what you want. If you have a hardware store nearby, it's relatively inexpensive.
Fair warning: it was vile.
She yawned lazily and said, "Please inform your misguided friend that we are not chattel. Thank you."
0. Yourself. If you die, all of the stuff below is largely irrelevant to you. Don't stick around, don't try to defend your property unless you've gone to great lengths to make it defensible.
1. Pets. If anyone leaves a pet behind to be burned alive, they also deserve to be burned alive.
2. Documents; titles, wills, deeds, insurance, medical stuff, tax stuff, identification, anything important. If you have a filing cabinet, consider just wheeling the whole thing out (if possible) and putting it in the back of your car, if there's a fire bearing down on you don't waste time sorting through stuff.
3. 24 - 48 hours worth of supplies. Water is essential, also consider food bars, batteries, and of course any medication. In fact, I'd consider having a go bag of this stuff on hand and ready to go every summer if you live in a fire danger area.
4. A radio. You need to know what's going on, and a radio is one of the best ways to do this during a fire.
5. Medication, again. Don't forget your meds, or your families, or your pets.
Once you have that sort of stuff in order, second priorities;
1. Get some photos of the inside and outside of your house. Insurance companies are scum and will try and get out of holding up their end of your policy however they can.
2. Collect up irreplaceable stuff like photos, hard drives etc.
3. Time permitting, move any fuel (as in stuff that burns) away from your house.
4. Time still permitting, block up your gutters and fill them with water. Also seal any windows as best you can and move anything flammable away from them.
5. As you're leaving, turn on all your sprinklers if you have them.
Ideally, you want to be out of there long before the fire is anywhere near you. We get told to make the decision to stay or go about 24 hours before our properties are threatened by the fire but it's not always easy to know when or if that's going to happen. But if you can see the fire in the distance I'd suggest going RIGHT NOW, and if you can see flames and they're reasonably close then it may be too late to leave safely.