Slight tangent ahead...and I realize that this is just my opinion and not everyone will agree. Apologizes for the "me me me" of this post.

Just some thoughts.
When it comes to running in less-than-ideal weather, I use the treadmill as a total last resort - it has to be crazy cold (like single digits), lightning, icy, etc. for me to go inside. Because what if there are less-than-ideal conditions on race day? Then what do you do when the treadmill isn't an option anymore?
For me, I NEED to know that I can run in less-than-perfect conditions. Relating this to Disney races...because while Disney is super magical and all that, they can't control the weather just yet...
- In 2010, most of us know that it snowed/sleeted during Marathon Weekend - snow/sleet in Florida. What if you had never done a run in snow/sleet? You'd panic, right? That's what training is for - you need to know that you can handle those conditions. Running is mental enough without adding in the pressure of running a loooong race in conditions you have never experienced before.
- Or how about Splash & Dash (Wine & Dine 2014)? Almost 13.1 miles of steady rain. I had run in the rain before, and while it wasn't what I would prefer, I knew I could do it because I HAD done it before - there were times during training where it was raining, and sometimes I'd avoid those days, but there were other times when I DID do training runs out in the rain. So the race was fine...I wish I'd had a hat with me, but overall, not a big deal.
- Or how about 2015 Marathon Weekend when we had a wind chill warning - temps in the 30s like we're discussing right now? Again, I knew I could do it, knew what kind of clothes to wear, because I had done it before, and it was fine.
I don't understand how you get this kind of valuable (in my mind) experience by going to a treadmill at the first sign of less-than-perfect weather, or by doing ALL runs on a treadmill - similar to how a treadmill doesn't prepare you for having to keep pace on your own (without the help of a machine), or running on a not-soft distance, or slight changes in elevation (unless you use the incline, I guess), or wind resistance, etc. If you're training for a road race, you need to know that you can run on the road and that your body can handle it - no matter the weather. Yes it sucks to run in crappy weather, but if you don't do it, how will you know that you can when you HAVE to do it (i.e. on race day)?
End tangent, and apologies for the novel.