Winter biking with kids in trailer?

I'm curious if anyone does winter biking with kids in a trailer? I have a two year old -- he loves the trailer in warm weather and I'd like to keep riding as much as we can through the winter.

Any tips on keeping the little guy warm? Bike trail vs road?

I ride an older Schwinn hybrid that is basically a commuter bike. I'd like to do our normal mommy commuting (short rides to library, classes) plus some longer (comparatively) rides for exercise.

We are in the Chicago area, so winter temps and snow vary widely.

Thanks!

I just bundle mine up and use all the covers on the trailer (so it's not open), but it's not nearly as cold here as it is in Chicago...

My friend has an 8 month old that she takes out on rides in the trailer. She just took him out on Sunday (it was in the upper 40's). He was all bundled up to the hilt with lots of blankets around. He mostly just slept, but would have surely cried if he'd been uncomfortable (I guess... he fusses when life isn't just right). I know 8 months and 2 years are light years apart, so I'm not sure how that would translate. I imagine if he's bundled up nicely and has lots of comfy blankets and toys, he'd be happy as a clam.
Oh, she did line the trailer with a very thick blanket- put it on both sides and across the top (on the inside- not sure how she attached it, tho I think she just tucked it under the metal frame). I guess to keep some of the warmth in? She left the front open so she could see him through the window.

Having taken kids XC skiing in sleds, here are a couple of things to think about
-they will generate very little of their own heat, so insulation is foremost. Think something like a sleeping bag as you do not want to constrict them.
-Extremities ( hands) are really prone to getting too cold as they like to pull them out of whatever you've bundled them it. This is why a sleeping bag type thing is good, you can close it up around the neck so the hands stay IN and WARM.

have fun

I'm in WI and tried it with my son when he was 3 - he hated being in it in the cold weather. I tried one of those round thermal heat pads the ice fishermen use for him to sit on but couldn't get him comfy enough.

So I waited til he was 4 and got him snowshoes:D He LOVES those!

+ 1 on what Irulan said. You will be generating lots of heat while they're just sitting still, so more insulation is required than you'd think. A sleeping bag sounds good. Remember it gets compressed underneath, so an extra layer of foam pad or something to sit in or underfoot is good. A quick way to add heat is just find a non-leaky water bottle and add as hot water as the material allows. Put it in a sock if it's hot enough to burn, then put it inside the sleeping bag or blanket. Refill with warm water anywhere you can if you're out for a while.

Here they typically say to keep outings to less than an hour, hour and a half if the temperature is below -10 C, and to not go out at all with small kids below -15 C (with kids sitting still in ski-sleds that is). I was also told that a good way to check body temperature is by feeling the back of the kids neck.