There’s this thing in B:TVS that used to drive me insane. Fortunately I have found a handy full colour photo to fully illustrate the issue before i go on:

i'm sorry the weather is what?
See, on the left? It’s Willow Rosenberg. In keds and tights and skirt and her cozy fuzzy sweater. Xander and Giles are enjoying a particularly brisk fall day and Cordelia is somewhere in the middle, maybe early September.
Buffy, however, is in July with a touch of boot. It never occurred to me (except when it was obvious) that this was because Willow was The Not Hottie and Buffy was the Hottie, which I suppose, in retrospect, is kind of a hai, duh, thing, but I always thought Willow was made of awesomesauce.
And it drove me crazy that Wil was in sweaters while Buff was in mini skirts and spaghetti tanks. I was all OMG AS IF PEOPLE IN THE SAME CLIMATE WEAR SHORTS AND SNOW PANTS ON THE SAME DAY.
Except I know of such a strange and magical place. It’s called “Canada”.
I can’t remember when I realized it, possibly on one mid-December day when someone walked by in shorts, or alternately a lovely warm spring day when someone walked buy in a toque, scarf and snow boots.
I’m still not sure the logic holds up in Sunnydale, but here? It’s amazing. One of the greatest things about my part of canada is how we
1) refuse to accept it’s getting cold and therefore will wear inappropriately unpuffied clothing well into the winter months and
2) refuse to be in winter anymore and suddenly around Feb/March, even though there could be snowy white upon the ground, everyone gets out their short pants and t-shirts and is all “screw it, I’m dressing for spring”
There really is a psychological change that happens and it’s got nothing to do with the actual climate.
And I have no idea why I thought of that, today, perhaps because I wore my short pants with a cardigan, but dudes, it gets cold in my office tower like what.