1. Toe or shoe covers
Cycling overshoes, on the other hand, engulf your whole shoe and see a cuff that will continue up the calf - the length of which varies by brand and model. Of course, the further up the leg, the greater the protection against the elements, and with the additional coverage, it should come as no surprise that full overshoes are considerably warmer.
2. Windproof or waterproof
Are you riding in the UK where there is a constant threat of rain? Or Colorado, where if the road isn’t covered in snow there probably isn't much precipitation to worry about, but the temperature is likely to regularly dip below freezing?
If the threat of wet weather is a constant, look for something made of neoprene. It does well to keep water out for a while, and when moisture inevitably finds its way in, acts like a wetsuit and keeps your feet warm.
Windproof shoe covers will have an internal membrane and are ideal for taking the bite out of cold winds. Booties with waterproof membranes are available too, but water has a habit of getting in anyway, and their neoprene cousins are usually a bit warmer.
3. Waterproof isn’t totally waterproof
Even if you have the best cycling overshoes on the market, your feet are still going to get wet in heavy rain. Water is a sneaky devil and will make its way in through the upper cuff and the cleat and heel openings in the bottom.
4. How to wear them
While most will argue wearing your overshoes should go over your tights, there's an argument for wearing them underneath. Water will usually land on your tights, then run down your leg. Wearing the tights on the outside of your overshoes will mean that this water doesn't run down inside and straight into your socks.
Talking of socks, if you're ever wearing your overshoes with shorts rather than tights (think rainy but warm weather), then you should avoid wearing socks that extend beyond the height of your overshoes. Many overshoes are designed to seal against the smooth skin of your leg to keep out the rain. Introducing a fabric sock ruins this seal and offers an open door for water to seep into your socks.
The other place that water tends to sneak in is through the cleat hole. Pairing your overshoes with a waterproof toe cover can help that water to run straight off your toes and onto the floor, rather than being soaked into the front of your overshoes.
The thicker the shoe cover, the warmer it's going to be, but one thing to keep in mind is how much of the bottom of your shoe it covers. Carbon is a terrible insulator which, combined with the metal cleat screws, can radiate cold into your feet and lead to discomfort. Unfortunately, there needs to be holes in the bottom of your cycling overshoes to accommodate the cleat and heel pad, but in most cases, the more of the sole that is covered, the warmer you will be.
Wrestling shoe covers onto your feet can be a workout all on its own, but well-placed zippers can make the process considerably more manageable. Look for a pair of cycling overshoes that feature a pull tab built into the heel to simplify the process. Velcro straps at the top cuff can allow you to tighten up the opening and help to prolong water ingress, but its effectiveness will eventually deteriorate.