Mid 50's, I would just suck it up. 40's--wear the shirt. Low 50's is exactly where I would be waffling. I am probably the most cold-phobic person I know--probably a combo of genetics
(Dad was a big guy in his prime, but the same way
), skinny build, and living for years in the tropics. For me it's not just a matter of comfort. Sometimes I get so cold that I have muscle spasms
(back and stomach
) or am shivering so hard I can't control the bike. My decision about the shirt would depend partly on how I feel when I get out of the water, and partly on how windy or sunny it is and what direction the weather seems to be going. At those temps, the shirt would always be there in transition; I may or may not actually put it on. It's a split-second judgement call that I've gotten better
(and faster
) at making over time.
For a typical Pacific Northwest summer race, it will be very cool in the early morning, sometimes as low as low to mid 40's, maybe low to mid 50's when you come out of the water, and then warm up to the 60's within an hour or two. As long as the sun is out, or on its way out
(morning fog is common
) and it's not too windy, I'll usually be fine with just the tri-suit, especially for a shorter event with higher effort level. When I might put the shirt on is if it's raining and windy. That means temps aren't likely to rise very quickly, and I probably won't warm up that quickly, especially in a longer race
(like HIM
) with more moderate effort.
My favored layer for that situation is actually a surf shirt with a partial zip
(keep it open in transition
). It goes on easily when I'm wet, is fairly tight-fitting, and I can easily push up the sleeves and pull down the zipper if I get warm. In more extreme conditions, I use a Merino wool base layer shirt with a partial zip--warmer but not quite as easy to put on when wet. I use it for training a lot, but think I have only worn it for one race--low to mid 40's and rain on the bike.