I have a target that is 24" tall by 12" wide, I will paint the top and bottom black and the center portion white so that I have a white rectangle 12" wide by around 8"-10" tall. I practice going out and making first round impacts in that. The condition/range/if I have a spotter dictate my max. With my best rifle, under great range conditions, as in little or no wind, I can make consistent first round hits on that out to 1100-1200 range, I would take a shot in that range if I couldn't get closer and conditions were perfect. If wind gets in the 5-10 range, or is inconsistent or shifty, first round hit percentage goes down significantly in the 1100-1200 range, and I would not take that shot personally. If my wind bracket is a 5-8, and I have a spotter that can watch the wind for me and tell me when to take the shot, and I can confirm what I'm seeing in my scope, I do pretty good in the 800-900 range. Without a spotter though, I will take some off of that, as I feel a good spotter is essential to consistent first round impacts. I have shot in winds gusting from around 15 to 35 mph several times, and besides the sand blowing in your face from prone making it extremely challenging to even get a good sight picture, making hits at long range is more luck. When the winds are like that, my max I will take a shot is around 400-500 yards, if I'm presented with a full vital zone shot, not quartering or anything, and if I can get closer at all (often possible because any and all noise is muffled) then I will. However, in high winds like this in open country, you can usually make good use of a of a wind meter, and try to bracket your wind and take your shot when it is in the area you doped for.
You just have to go out and practice to establish what your max is, and NEVER skip a shooting session because the winds are bad!! This is the best time to practice, and will really help your skills and teach you. Are you going to stay at home and not go hunting because it's a windy day? Likely not, so practice in those conditions too. The only time I will postpone a range session due to wind is if I am doing a ladder test or some other form of load development, because the point then is about the rifle's performance, not my skills.