A couple of times I have done two separate fittings before getting dialed in and making my final selection. Not only can the conditions of wind and temperature make a difference, I find there are days when I just don't have the swing working very well or just the opposite, I am killing it on fitting day and my normal swing will not produce nearly the same results. I guess I would recommend anyone getting an expensive fitting make sure the weather will be decent. That's probably why the TPI west coast is in Oceanside. Odds are pretty good for nice weather.

This has happened to me in the past with a Titleist product specialist at a Titleist Thursday fitting. It was windy the day he fitted me for my 917D and when I took it to the course it just was not right when I got it. He lives about five minutes from me so when he was doing the fittings again, I took it back to him and he reset the lofts and long and straight. Best to do it on a one windy day. It was my fault because I wanted to get fitted that day. Haste makes waste as they say. Bill is the best. You want ideal conditions if you are get fitted outside.

Well, since you NEVER play golf indoors in perfect conditions, I wouldn't say that is an optimum environment either. Neither is hitting off a mat of any kind. Outdoor fitting, even with a little wind (10 to 20 MPH is pretty normal around here at least) is better than strictly looking at numbers on an indoor launch monitor. Ideally, using a LM in tandem with an outdoor fitting off grass is the way to go. If there is too much wind (like a steady 25 mph +), let the fitter know that you would prefer to do it another time. I don't think that's too much to ask if you're spending $1,000+ on new clubs.

If you're like me, every day is a guess on how you're hitting them. You don' know until you start warming up. You just hope the day you get fit is a good swing day.
The fitting is to determine what works best for your swing, not for the weather. Whatever they come up with in the wind is probably the best combination in calm weather too.

Hey Guy, Totleost fitter here in DFW. Fitting on windy days can be a challenge. In my opinion it’s harder on the consumer as the wind tends to play a part with their swings/balance. As far as trackman, we normalize the environment so it takes outside conditions out so the algorithm calculates the data as if it’s normal conditions. As I seen in other comments swings tend to change when it’s windy conditions which will be different when they get their clubs and swing in normal conditions. Hope this helps as far as your main question in regards to Trackman.