Probably anything under 15 degrees F is to cold
Depends on on the quality of the ground. If it's so cold that the ground start's to get hard and frozen you should not jump. When the ground is still good I don't know what should stop you from jumping.
It really depends on what you think and want to do
I would say anything under -20celcius it rlly depends on u and ur horse and ur beliefs
I think it depends on whether or not your indoor is heated and also the footing. I have an indoor that is not heated and is open and I don’t ride under 25 degrees Fahrenheit. However if you are jumping and the footing is hard and frozen, don’t jump.
It depends on the footing I think. If it is so cold even the indoor footing is freezing up/getting hard and solid I would skip jumping until it's less cold and the footing is back to normal. When it's cold always make sure you warm up your horse properly before starting to jump, and take your time to cool down the hprse afterwards.