It's true that sometimes the weather is just not user friendly when it comes to walking outside. Dangerously cold temperatures, blizzard conditions, or icy walking routes can make it almost impossible to walk outside safely. And why risk your health to workout?
The best solution is to have a go-to indoor walking route in the location where you spend the most time. If you're a work-at-home person like me, that route can be as simple as up and down the stairs for 25 minutes--that's a workout, trust me. Or if your home is one story, the hallway and routes through connected rooms does just fine.
If you go to the office every day, look for long halls, stairs, and empty conference rooms to get in your laps.
The other great solution is your local mall. Many open their doors to walkers prior to retailers opening for business. This creates wide open walking areas that you might really enjoy. Granted you'll have to brave the weather to get there but once there you're in a heated location with facilities. That's not bad for a bad weather day!
If you know you'll have days when the weather is just too dangerous to be outside, prepare in advance by sleuthing out your best indoor routes--at home, at work, or at your local mall. Come springtime you'll be so glad you've been walking and you will welcome the warmer temps and better conditions with open arms and happy feet.