Winter Riding: How cold is too cold to ride?

You serious? did you mean farenheit? Cause 30C is getting kinda hot..

That was MINUS 30 C = -22 F, which is a bit on the chilly side.

I'm not a fan of the cole below about 15-20 F, but my horses will run and play all day in that weather so I wouldn't be scared to ride them. I mostly worry about too hot to ride

I fly to Canada to teach some clinics. Last winter I went in JANUARY. Man, it was cold. One morning it was 9 degrees F. We were in an indoor, but not heated. At least we were out of the heavy winds that were outside. The clinics went very well. Mostly flatwork until later in the day when things were a bit warmer. Lots of warm-up and lots of cool-down. We never worked so hard that the horse was drawing in masses of cold air into their lungs.

This year I will be there in mid December. Hope it's a bit warmer then!

I have ridden in some brutal temps, having been born and raised in Northern MN; I didn't do anything 'hard', but it was so cozy hopping on bareback and going for a nice slow jaunt. Cold doesn't necessarily bother me, but I don't usually ride when it is extremely windy AND cold.

I usually stop riding once there's snow/ice on the ground. The hill/lane I live on is treacherous even for the best of 4WD vehicles, and since we don't have a barn and the horses' shelter consists of the woods and a open stock trailer, they always get snowballs built up in their hooves; I figure that I'll just let them be, and not put any undue pressure on them to perform. Myself, I'm generally unaffected by the cold; I have a higher body temp and used to work at a Ski resort, fixing the snow machines all winter, so it takes a lot more for me to get cold.
This winter, I'm planning to take Bandit and maybe Dante down to the local arena as much as possible, to work on their driving, though. I'm looking to find them some quarter sheets and trailer sheets, just as a precaution.

Well up here in the frigid North, we're used to getting temps down to -30C regularly from about December-February. We will usually have a cold snap for about 1-4 weeks where it can get down to -50C including wind chill.
My horse is blanketed during the day when he is turned out and lives in a heated barn overnight that is in the same building as the arena, so I ride all year round.
When horses are on outdoor board and well blanketed with good access to hay and a shelter then generally we'll ride them if it's around -20C during the day. We won't ride them at night however, and we blow-dry them before turning them back out.
When they are outdoors and un blanketed, they usually get the winter off. We'll ride outside during the day without a saddle and won't get them sweaty occasionally.

Nothing like a furry warm horse when it's cold outside. I'm not as concerned about the cold as I am the ice under the snow. But, I take it easy when it's colder outside and give them a nice long cool down.

Like others, I'd say I wouldn't ride in about -30°C. We don't get that cold often though, thank all that is good for the Gulf stream

Humm...

"Dashing through the snow
In a one-horse open sleigh.
O'er the fields we go..."

So I guess it must be doable. Though I always did kind of wonder just how the horse managed it.