The increase in temperature won't really be that noticeable from a "lived" point of view. It's only a few degrees, after all. The real problem is that those slight increases in temperature affect sea levels, which fucks over every town on every coast, and fucks over inland portions of California (Sacramento and Stockton), Louisiana, Florida, Virginia all the way up to D.C. along the river, same for Philadelphia and Trenton, and much of the Hudson River valley in New York all the way up to Albany.
(if a 7 meter rise:
http://geology.com/sea-level-rise)
Of the major cities above 1 million in 2044, if there's a 2.5 (let's round that up to 3, b/c of the interactive map's options) meter rise as a quick google search for "sea level rise by 2040" suggests is anticipated regardless of policy changes, these cities would be affected:
Destroyed:
New Orleans
Charleston
Stockton
Majorly Affected:
New York City
Houston
Cape Coral
Hampton Roads
Sacramento
San Francisco
San Jose
Seattle
Affected:
Tampa
Jacksonville
Philadelphia
Boston
San Diego
Providence
Portland
Sarasota
Riverside (inland empire, Indio/Palm Springs area)
Minimally Affected:
Los Angeles
Miami
Orlando
Richmond
D.C.
Baltimore
Hartford
Oxnard
So, no, Seattle and places to the north are not where you want to go. You want to go ... to Austin, oddly, away from the coast where the temperatures are still fine and with a booming economy and green energy attitudes. Austin is primed long-term to be weather the economic externalities of global warming.
If you double that to a 6 meter rise, Sacramento and significantly many more parts of the East Bay are now completely destroyed, Cape Coral is now totally destroyed, Miami goes from workable to a complete disaster area (though not totally destroyed), among others.
And none of this even considers the many smaller cities that are economically significant ports, tourist destinations, or otherwise meaningful cities and will be for the foreseeable future. At a 3m rise, Savannah, Myrtle Beach, Wilmington (both NC and DE, but the latter is a core city of the Philadelphia MSA), Portland (ME), Albany, Panama City, Pensacola, Mobile, Gulfport, Beaumont, Brownsville (and I' sure the effects would be felt in the McAllen/Edinburg area as well), and Olympia.
So not only are there major populated areas that are affected, but there are a significant number of small towns the cumulative population of which is equivalent to a large MSA that would have to be evacuated as well. And this doesn't even get into the broader economic consequences. The central valley of California's inundation and fundamental alteration of water flow patterns would have world wide consequences in food distribution, as that region currently produces a huge 8% (that's an economically important %) of our nation's food output.