How cold is to cold to ride....

I live in Minnesota and it can get really cold. I have heard from a few people that if it is less then 10 degrees that you should not ride because it is not good for the horse to be breathing in that really cold cold air. I have an indoor arena but it is not heated just a tin building. I am going to ask the B/O to put up a thermometer in it so I can see how cold it can get, but I am just wondering if anyone else knows if this is true or not?
Thanks

Goodness, my horses would be dead a million times over.
I have found nothing wrong with working horses in sub-zero temperatures. I usually don't want to ride in anything lower than -20*C now, but when I was younger I'd ride up to -40*C - I'd just bundle up!! All I had to ride in was a tin arena as well, no insulation or heating. We worked our horses hard, too.
Now I'm a wuss... haha!!
I would suggest using a quarter sheet during work and a cooler afterwards so the horse doesn't cool down too fast and catch a chill - and of course make sure they're pretty dry before you turn them out again.

..ahh fond memories of horse's sweat evaporating then falling back down on us as snow... haha

CRAZY NORTHERNORS!

I'll be completely honest...I don't ride if it is below 30. Granted I'm in Tx and it rarely gets below 30 in the daytime

I've been told that horses don't start using calories to warm their bodies until temps are in the teens. So if you rode in colder than that make sure you're feeding enough for the "double duty" of the horses body. Other than that I don't see any problem with it.

I have always been told not to ride under about 20*F and if you do be very careful not to work them too hard so they start sweating..And if they do be sure they are dry before you put them away.
I'm not sure though. When I do ride in the winter I just take it easy on them.

well, I'm in Georgia, and we ride so long as the ground is not frozen. We don't have an indoor (there really isn't a need for one with our temps.), but if the ground is hard, we don't ride (usually below 30)

I'm a sissy in the cold so I'm really bad during the winter, but my thoughts are, if the ground is frozen, then I shouldn't ride......

My mom and i used to always ride in the snow ... it was so relaxing and our horses never had any problems ... we just didnt work them hard at all ... it was usually just a pleasure ride at a walk

I ride all the time in the cold and my horses have never been worse off because of it. In the winter, I don't ride them really hard anyway and not for very long because I am kinda a baby too. Anything below zero is too cold for me although my horses don't seem to mind. The only thing I watch out for is ice and ground that has been muddy and has frozen in the little spikes and peaks like a mountain range. I tend to avoid that because that can damage hooves. Other than that, I don't see anything wrong with it.

I ride all year-round, but if it's like under 20 or 20ishF I don't ride. Instead I'll groom or something. But on cold days (not as cold as 20ish) I always do a long warm-up & cool down; & not too heavy on the work.

Thanks all for responding, and to all you southerners!!! LOL. I use to live in Va. Beach so YEEHAW, thats great weather to ride in!
Hotreddun, you make me role on the floor!!lol
Poptart, ya that is kinda of my thoughts, I have always liked to go out to groom on those really cold days, but it does take alot longer to warm the horse up on the other days.
It is 22 degrees today, and feels really nice, but there is no wind. But I am sure we are going to have a cold one this year!
JDI and Rustic, you guys know exactly what I am talking about!! So as long as I am being a good horse mommy, other then that there is no reason not to ride. Thanks I was just worried about his health, breathing in the cold air since I had been told that it was not good for them.
Thanks again guys!