How cold is too cold for children to participate in outdoor sports practice? is 34 degrees safe? any time restrictions or precautions?

If they are dressed: warmly enough, that is not too cold, unless they have a medical problem which could be exacerbated by the cold. If not, they should dress in layers, so that they can remove some of the outer or inner layers as they get warm running around. If they are too warm and sweat, then cool off, they will be even colder. The other precaution is keeping their toes and fingers warm enough.

Healthy outdoors!: A child in robust health is quite safe outdoors in that temperature. He should properly attired for the weather. There are medical conditions or instances of acute illness that may make it unwise. In cases of extreme adverse condition the general advisory will be a suitable guideline or anyone.