If you encounter a cluck who thinks that real cold temperatures and blizzards prove that Global Warming is a myth, link them to this page which explains why not. It probably won't do any good because they're going to believe what they want to believe…but give it a try. Can't hurt.
And note that these people are the same people who, every time an election doesn't go their way, insist that it was rigged and there's proof that tens of thousands of illegal aliens voted. And their "proof" is usually something like, "My guy couldn't have lost fairly. Everyone I know voted for him!"