Not scientific, but still valid
Wow, the thread on VFFT has been running since September!
You can compare average temperatures from one place to another, but how does one weigh temperature with, say, wind speed? There's no formula that factors the several components of weather to quantify its badness. So the claim "home of the world's worst weather" is a subjective one, but a defensible one nevertheless.
There's a great deal of nuance to weather severity. For instance, a 100 MPH wind on Mt Washington would be far more powerful than the same wind at Everest base camp, which would itself be more powerful than the same wind on Everest summit. Why? Lower altitude means higher pressure. Higher pressure means more air molecules beating against you. It's like the difference between standing in front of a garden hose and one of those pitching machines... kind of.
Even if you could plug wind speed, air pressure, and temperature (etc) into a formula to calculate "weather", would you use calculus to factor in rates of change? July 2, 2004 had a peak gust of 124 MPH, which isn't that spectacular for a place that has hurricane force wind 100+ days each year. What made July 2, 2004 so special was that the average speed before and after was about 50 MPG. The gust came out of nowhere. It's hard enough comparing the peaks and the norms, getting from one to the other is a big part of the big weather picture.
Of course, we aren't counting the weather in places we don't measure it. What about thunderstorm junction on Mt Adams? What about Rainier or Denali or Everest? What about an arbitrary spot in the middle of Antarctica? Saharan Africa?
The designation "home of the world's worst weather" is anthropocentric for sure, but you sticklers can tack on "that we know of". Try to fit that on a t-shirt, okay? :-)