The only online place I suggest is www,Uggsaustralia.com if you aren't buying from authorized dealer at mall. I hear they aren't good in rain, sleet, heavy snow, but ok in light fluffy snow, not warm in frigid temps. Comfy.
You can buy them several places, just goggle Uggs and different websites will appear. You have to treat them because they are suede so they will get water marks. They are super comfortable and keep your feet warm as toast!
Pretty much any department store or shoe store. And if you spray them you can wear them in snow. I really wouldn't recommend wearing them in rain unless it's just from the house to the car to the store
Lots of stores sell them. I live in Minnesota and I wear mine in the snow all the time, just if you don't want salt stains put some sort of protectant on them and i wouldn't wear them in the rain your feet would get wet way to fast.
Uggs really aren't ment for wet weather. At the Ugg store they have a kit which contains 3 sprays and a certain type of brush with four sides of different ways to brush your uggs on the outside. The sprays are a sheepskin protector, a sheepskin cleaner & conditioner, and sheepskin freshener. The sheepskin freshener is used on the inside of your uggs after every wearing, just spray once in each boot and let it dry and your boots will be ready the next time your ready to wear them(: hope this helps!