21 miles means you live out in the relatively far "newer" suburbs rather than the older suburbs. That means the your public transportation is limited to the train or taxi. The only real options for you to go from Chicago to home are:

1. Personal vehicle
2. Train (Metra or similar)
3. Taxi
4. Buses (plural - there may be a network that can get you there but I've never heard of folks doing it)
5. Bicycle - you'd have to stick to less travelled roads - they exist if you plan ahead, but you'd need to bicycle there in Chicago when you need it.
6. Walk - figuring 3 mph, having to go along side streets, as opposed to major highways, it could take 10-12 hours. With the weather we're having today this could be a nightmare.

Quite frankly the best bet might be to bike or walk out and hope whatever hit the fan is less of an issue as you get away from the city - allowing you to access transportation or have friends/family come and get you.

Or ... just hunker down in Chicago and wait for things to calm down.