I found this statement baffling, but kept my mouth shut because I'm already the "difficult one" at work, and I wasn't willing to make that worse by arguing about weather words. Besides, that's what the internet is for!
So, coworker who was totally wrong about the weather, but still a great person: this *is* fall. And yeah, every year is a little different, but I don't think this one is super weird. We've had cold days and hot days, sunny days and rainy days. The leaves are changing color. It's fall! (My favorite season, so let's not have any more talk about skipping it!)
(PS: In other somewhat humorous work news, we got a policy announcement back in mid-September that may or may not limit our ability to work from home on a non-work computer, among other things. I asked my boss about it. She had not considered this implication. She said she would look into it. I have heard nothing about it since.)