Another vote for "treat them as individuals." I have one who would never wear a blanket unless it's raining, another who shivers on a windy 50 degree day, and another who is tense and tight and miserable under saddle if he doesn't have something warm over his back any time it's much less than 45. And they all have full coats, and we live in Wisconsin, where it can be 50 degrees and windy in September. I actually look forward to Real Winter when it's below freezing for days at a time and I can just put them all in heavies and leave it that way!
We usually do not blanket our 20 yo Clyde x mare... but I make an exception when it is very wet (thanks Sandy).. She goes out for long hours and there is no shelter in her field. Cold and wet, she gets a rain sheet. This year though, we decided we were going to blanket her in the winter as well. She wears an Amigo XL rain sheet (which fits her perfectly) and we are getting the medium weight t/o when it gets colder. If needed we can get the insulator to fit underneath.
I'm in FL and my ponies were all blanketed the past few nights. When I'm cold, my horse gets blanketed. Same goes for my son and his sweater. We do body clip because we get such warm days and the fuzzy horses get sweaty and impossible to dry - so we have to blanket at night.
I was thinking the fuzzy unclipped broodmare would be happier without a blanket but she was huddled up and shivering all day long, trying to stay out of the wind so she got a blanket too, and she was a much happier girl.
After seeing an unclipped TB violently shiver at 55 degrees I became a firm believer in blanketing according to the individual. We have a horse at the barn that wears a 150g blanket up to 79 degrees. That absolutely blows my mind. However he is cool and dry underneath his blanket and seems happy and active.
No one on this forum knows your horse the way you do so I think you should trust you judgment. Unless your horse is prone to overheating then being a bit overly protective won't hurt a bit.
The low tonight is 30. My mare is inside wearing a medium weight. I am sure she would be fine in a sheet but she certainly won't be overly warm. At 30 I could do a sheet and midweight without her getting overly warm.
Our horses stay out 24/7 with run-ins unless the weather is bad, but they are all individuals. We have a 7 year old Arab that my daughter purchased as a yearling. We learned our lesson early, he needs a blanket in the winter. He also requires his own heated water bucket. It's not worth the colic because the water is too cold for him to drink, nor the weight loss when he gets a chill. The worst part is that he hates to be blanketed. I have a paint that doesn't keep weight when the temp drops below freezing, and the OTTBs, well, they opt for the barn and a blanket when it gets wet and cold. The old guy doesn't understand why we think he should wear one when its wet out, and one night in is all he can handle. The Canadian Sporthorse, well he's a real tough one along with the mule. These two think we are nuts when we pull out the blankets. I get some criticism for blanketing, but they all winter well and are ready to go back to work in February .