How to size a window header?

[nopermit]

I want to add a window to our basement. The header must support the main floor above plus the roof. I live in the pacific northwest so we experience snow loads. Is a double 2X8 enough for an opening approx. 48" wide?

 

[mmatthew]

The answer to your question is dependent upon several other pieces of info you have not supplied: 1) What is the tributary area of the floor and roof load that this header will be supporting? 2) What type of wood will you be using for the header?