If you want to keep your toes warm while cycling on a chilly morning you need to buy a pair of toe covers. While there are many good toe covers for cycling shoes on the market, the Performance Toesties covers are probably the least expensive. Sadly, they are also an example of getting what you pay for.
Performance Toesties are made of neoprene fabric and are both windproof and waterproof. These covers fit over the end of your cycling shoes, even if you are wearing cleats, and actually do a decent job of blocking the wind and keeping your toes warm. Because the covers are thin you can easily put them in your jersey pocket when you don’t need them. I’ve used them with both Look Keo and Shimano SPD cleats.
The major downside of Performance Toesties is that there is no reinforcement on the bottom of the covers. If you walk very much at all in these covers the neoprene will start to shred. Not only that, but every time you clip in you will probably do a bit of damage to the covers—it doesn’t take long for them to wear out completely. I look at these covers as being disposable after a dozen or so rides.
Performance Toasties retail for $15 and are available at Performance Bicycle (both online and in their brick and mortar stores). The covers are available in four sizes: S (6.5-8.5), M (8.5-10), L (10-11.5), and XL (11.5+). I have found these covers run a bit on the small size, so you might want to order one size larger than your shoe size.
In my opinion the best toe covers on the market are the Planet Bike Dasher Toe Covers. These covers are a bit more expensive, but I think you will get a lot more use out of them.