Pressing shift three times is clever… but way too clever. Even if you stick a giant popup saying "hit shift three times to quickly exit" I'm not sure anyone in a panic will remember—loads of people don't even know which key is shift, especially when there's three buttons on a keyboard that look the same and only two are the same. I've come across people who always use shift-lock and did't realise you could use shift for anything. I'd be interested to know what UX tests they actually did, and who with.
If I was going down the press a key three times, I would have gone with pressing any key three times apart from the number keys (plus an info box when you enter the page—"hit any key 3 times to quickly exit to the weather"). Most people, I'm sure, would mash the spacebar in a panic but if they missed then it would still work.
What I would have preferred to test would be 'mashing'/chording — pressing more than one non-modifier key at the same time, so a user could just smash a load of keys at the same time in a panic.
Going to the Weather page is a great idea, though.