It goes, translated very verbatim: "there is no bad weather, only bad clothes". It's far snappier in Swedish where it rhymes, but I guess the point comes across, still.
Update: after reading a few more comments, I guess this doesn't address the other end of the spectrum, that it can be too warm/humid to go by bike. Score one for cultural bias.
However, the Scottish Highlands do excel in miserable drizzle that falls continuously for days, weeks and probably months ("dreich").
And yes, I am Scottish and have spent a lot of time outdoors!
He rounded of his rant with the statement: "There's no such thing as bad weather, just the wrong clothes."
To this day I consider that quote to be one of my all-time favourites as it really helps me smile whilst most people are depressed over the fact that it's cold and wet.
Now, on the other hand I've had times where it's just downright miserable, and I was pretty sure my fingers were on the verge of serious frostbite, and that was NOT fun and never will be. But, that's not too common.
Getting soaked on the way to work can be a pain, but if one just carries a rain suit in his/her bag then this will never be an issue.
I've got a pair of those and they are really convenient: I can put them on quickly, even while wearing shoes, and my legs don't get as sweaty because the rainmates are open in the rear side.