I went to my Credit Union yesterday and I asked them if they offer a checking and/or saving account in Canadian Dollars. Unfortunately, they don't offer such account.
Where can I open one? Is it possible?
I'd look into HSBC. They operate in Washington as well as across the border in BC. If you can't open a CAD account locally, they can help you open and manage one in Canada from the US. It may or may not require having a small business account instead of a personal account.
If you can make the trip to BC yourself, I'd recommend opening an account with TD. They are apparently the only Canadian bank that will allow non-residents/citizens to open an account. The customer service is great and they have a good online banking site that should allow you to manage it from the US.