Reddit mentions of Sugoi Men’s MidZero Tights

So the rule of thumb is to dress for about 20 degrees warmer than it is outside. This means if it's 40's you are still in shorts. Some people can tolerate the cold better and the wind is also obviously a factor. So these numbers obviously vary by individual.

Somewhere in the 30's you switch to pants, some people don't do this until freezing, I personally do it in the upper 30's depending on wind.

Once we hit freezing and especially once there's a cold breeze you will want to start layering up on top. A base compression layer and a wind breaker. Or a base layer and a fleece.

Somewhere in the 20's I switch to wearing tights instead of pants. There are different thickness tights out there, thinner ones in the mid to low 20's. In the teens I put on the thicker tights made for running in such conditions. I use a pair of Sugoi midzero and Sugoi sub zero tights and some random target ones as well. I've used the subzero tights in runs under 0F and they work as advertised (and ran a 50k in 6F starting temps in them).

Outside of tops and bottoms you will need something for your neck and face as it gets into the 20's. I recommend the buff's made for winter running, they can also double as hoods or face masks. Once we hit the teens and single digits I also start wearing a balaclava. Then there is wool hats, wool socks and most importantly running gloves and mittens for colder temps. You really want specialty mittens, they made a huge difference and you can also bring chemical warmers to hold onto if it's super cold.

For shoes regular road shoes seem to work just fine, socks matter more, in icy conditions I put on a pair of microspikes over the shoes for traction.