How cold can you stand to be outdoors? The plane can take it.

Of more concern is going to be the wind. I've spent a winter up near Chicago... When the wind's howling at 30 to 50 mph you aren't going to want to fly, especially as a beginner.

You want to find a day when the wind is under 15 mph. (less is better when learning) After you have some experience... the only limit to the weather you can fly in is if you want to stand in it. I've flown in snow, sleet, rain... It doesn't really bother the airplane. (well.. freezing rain may cause ice buildup on the wings and cause a crash, but I doubt you'll want to stand outside in those conditions.)