1. Go out in the cold (and possibly wet) weather where riding may be uncomfortable.
2. Join a fitness club (at considerable cost) and start to train indoors or take spinning classes. Now some will go on a regular basis, but for the rest of us it's less likely.
3. Give up and take a rest.
4. Buy a home trainer and keep up your riding inside when the weather is inclement.
With the last option, a stationary trainer, which is designed to support the rear wheel of your bike and apply resistance to the tyre or rim, achieves a similar effect to riding your bicycle outdoors. It allows you to change the gears of the bike, to offer range of riding resistances.
If you use a 'Minoura Rim' trainer you do not have to change the rear tyre to a 'slick tire' to use on the trainer. The Rim trainers work with mountain bike or road wheels alike.
Using a resistance trainer has a cost advantage, you can use it anytime, you don’t have to make time to go to a gym and you can even watch TV or listen to music while exercising.
When listening to music or watching TV it is desirable to purchase a type designed to minimise vibration, the main cause of resonance (leading to noise). In summer it folds into a small compact unit for storage.
So why not go out now and purchase a stationary trainer so when the inclement weather sets in, you’re set up!