If I had to make an educated guess, I'd say that I probably wear a tie to work about 90% of the time. When the temperature is blistering hot in the summer, I get away with open collars a lot more often, but in the winter it's pretty much steady tie for months.
That said, I don't always wear a sport coat. There are days in the spring and summer that I pair up a long sleeve shirt and tie (sometimes with a vest) with a cotton canvas, denim, or even leather jacket then shed said jacket while in the office.
Today was one of those days, and I broke out a cream-colored Ralph Lauren medium-weight cotton number I'd picked up in the fall.
It's a nice solid cotton canvas number that works well both on the cooler ride into work in the morning while breathing enough to not make me break into a sweat on the way home. Here, I paired it up with a cotton striped blue shirt and Ra La linen tie in baby blue.
The cut of the jacket isn't perfect, as it's a size XL, which fits in the arms but leaves a bit to be desired in terms of the fit around the midsection. It's not completely slouchy, though, and goes nicely with a pair of chinos and a canvas/leather belt. I could probably find a slimmer cut jacket that also fits my 37" arms, but it would probably cost me more than $2.99 (and maybe I'll find one yet and retire this one).
Speaking of sport coats, if any of you readers and fellow thrifters run across any nifty lightweight (linen or cotton or something similar) ones in size 42l (or 42xl, as I need at least 27" from shoulder seam to arm opening) for a reasonable price, gimme a holler. I'm looking for a couple more decent late spring and summer weight numbers to add to my arsenal and everything I've run across in the past six months is either trashed or way too short (in the arms) or way too big (in the body).