43° for the commute this morning (less than 1/2 hour). I wore shorts, wicking T shirt plus short-sleeve jersey, arm and leg warmers. Above 45 I don't need the leg warmers. Below 40 I sometimes put on sweat pants and use a long-sleeved jersey layer.

I almost never have a jacket or anything insulated, the recent Atlanta-stopping snow storm and 4° being the exception, but I frankly overheated in those two events. Three layers of technical fabric, with two of them long-sleeved, does it for me. If I'm feeling like I might not keep the effort at a warming level or it's in the 20's I'd add a windbreaker on top. Below 20, this year I'd wear a thicker windbreaker over the 3 layers, that would be when I'd wear tights if I had them.

As has been said earlier in this thread, everyone is different. I wear shorts from 55 F and up, and knee warmers under 50 F. 50 - 55 F is kind of a "tweener", and it depends on the day. Sometimes on those days I will start out wearing the knee warmers, and taking them off at the first opportunity, and sometimes I just roll them up and keep them in the middle jersey pocket. Since the knee warmers can go to mid-calf (about the same length as knickers), I dont have tights. My legs generally are warm enough with knee warmers.

Tights of varying weight all year. I don't like the idea of skin cancer. I spent too many years out teaching fly fishing for a living and was in the sun for untold hours. These days, I stay covered up as much as possible.

Ride at night. Problem solved. Sun screen not required, but bug repellent in the summer months is a wise investment. Besides, evening is when you'll
see young lady joggers, out jogging in short-shorts.

Monday was "one of those days" in the Boston area. It started off crisp. By noon, it was still unseasonably cold. And then.... The southwest wind kicked in,
and the temp rose slowly all afternoon, until it was 74 degrees by five o'clock. Maybe not so great for Marathon runners, but fine for cyclists.

Above 45, shorts. Below, tights.

In Honolulu, we ride in shorts and T-shirts year round. You northern guys have all the toys.

This old poop dont like to ride unless it is at least 65 and I can wear shorts. I just dont like to ride with long pants.

In Oregon, on average, there are more days in the 40-60F range, waiting for days over 60F would mean the bike sits most of the year.

Actually, I really enjoy the seasonal changes in weather and having the right gear allows me to ride all year in relative comfort. Call me strange, but riding in cold or wet rain while protected from the elements with the right clothing is extremely enjoyable and gratifying. Also takes me back to my youth; where I feel like a kid once again without a care in the world. In other words, it can be downright FUN!

Remember, knee damage occurs over a long period of time. Knees that don't ache today or don't feel chilled means little short term. Wear is still occurring at low temps whether one is aware of it or not.

Tonight's ride was yet another of those occasions where I felt I was over-dressing, but was glad I did. 64 degrees felt more like 44, with the wind. And, once the sun was gone,,,
Well, it felt more like early March. I can tell, this is going to be one of those springs-that-isn't. It will be nasty until about the second week of June, and then the
temp will skyrocket, and non-hot weather people will be groaning about how hot it is.

No hard fast temperature barrier for me. It varies based on sunshine, wind and wind direction, humidity, the planned route, how I feel.
Definitely I put tights on when it's 53F or cooler. Definitely I wear shorts when it's 65F or warmer.
My calves get colder before my knees do then get tight and crampy. My pudgy knees are well-insulated. The knees also swell and get stiff when they are hot and sweaty.
I have several weights of tights that I wear over shorts. Thin running tights, then unpadded cycling light-fleece, thick-fleece, or am-fib/tri-flex as temps drop.
The thin running tights roll up small and pack light. If I think they will be shed I carry an ultralight drawstring backpack to carry them in.
And yes, tights over shorts help minimize laundry. Shorts need to be clean each ride but tights can be worn several times between washes.

I am considering purchasing wool knee warmers. I would wear those for temps below 40, or if rain is forecast for temps in the 50's or cooler. I have lycra knee warmers now. This year I was impressed with the smart wool arm warmers I have, and the ability of them to keep you warm even if they get wet. It seems a logical conclusion smart wool knee warmers would be good as well.

Here's what I do: create a database of what the weather was, what you wore, and how it worked out. For example, one of my entries is:

I start riding when there is no more ice on the roads (temps above 32F).

32-45 tights over shorts.
45-55 knee warmers + shorts.
55+ shorts.

It's a crapshoot trying to figure out what to wear during the spring. If it's sunny, it can turn a cold temp into a warm day. So what I do is carry my Bolder Bike Packing saddlebag that can take from 3 to 6 liters. I then dress warmer than I think I will need and two miles in, I make the decision and move something to the bag if needed then ride on.

J.

fwiw I've read, at 50 degrees or lower, cover the knees

The locals are divided when its warm enough, over 70f, for shorts.. its rather too hot.

and I lost track of my sunscreen in 6 months..

45-62F leg warmers

Below 45 Tights

Above 62F shorts

Always remember one thing, you can always take if off but if you don't have it you can never put it on

Ride and see what you like at what temperatures. I'm a list maker and have a spreadsheet where I enter everything I wore on what rides at what temperatures and conditions. I get the temperature range off my Garmin 800. It's too much for my aging brain to remember and the amount of moisture, wind, and cloud cover makes a difference. I also try to layer with stuff that fits in a jersey pocket because there's not one answer.

+1

Speak for yourself ... I ride over the Pali at night and in the early morning and it can be in the 50's some times ... I've put on the leg warmers in those conditions ...

Going back to the 1970's

The old school of thought from the Guru European Soigneur's, 65-67f was the cut off, below this and it was leg and arm warmers, above shorts were OK.

Once it gets below 50f I prefer to be warmer rather then colder, Growing up here in Canada you can bet we definitely rode outside in some ridiculously cold temp's