While the U.K. does have its occasional sunny days in between the rain, driving with sunglasses on can net you a fine of £2,500 ($3,400). The Chronicle Live also notes that you can get an additional three to nine penalty points on your license for the practice.

The law stems from the understanding that driving with sunglasses might impair your vision. Poor vision can lead to accidents with other motorists or pedestrians.

The opposite argument could be made as well. If you're driving on a sunny day, the glare doesn't help you notice what's coming in front of you and could distract you to everyone's detriment.

In that case, driving without sunglasses on certain occasions can land you a £2,500 fine.

So what are drivers supposed to do in this situation? It seems like a "damned if you do, damned if you don't" decision. The details are a little more complex.

The type of sunglasses matter

General-use sunglasses might be a bit too dark to drive with and are considered dangerous for drivers to wear while out on the open road. The U.K. Automobile Association recommends that drivers stick to two types of sunglasses – fixed and variable lenses.

Variable lenses are like transition lenses that react to incoming light. The brighter it is, the darker they get. However, there's a catch. Some variable lenses react to UV light, while others use visible light as their cue to change.

The AA suggests using visible-light-triggered lenses, since most windscreens filter out UV radiation. On the other hand, fixed lenses always remain at the same level of tint throughout their existence.

The level of tint needs to be at an acceptable level, and having too dark a pair will get you fined.

Category two lenses

Many fixed sunglasses are "category two" lenses that filter between 18 percent and 43 percent of incoming light emitted by the sun daily.

These do not filter out the most harmful rays. For that, you would need something like polarizing lenses, which filter out up to 50 percent. You can quickly check the filter level of your glasses since most U.K. lenses come with their filter levels easily readable on them.

While the safest bet would be using clear lenses, it's not always ideal for when you're driving through a sunny day.

Instead, it'd be far more viable to have a variable lens that can adjust to the ebbs and flows of the sunny day.

Before getting into the car to navigate through the sunlit roads in the UK, make sure and check your filter level on your glasses. The light filtering scale is a very fickle one, and the AA mentions that driving with anything that offers category four protection is virtually useless. Having the right category could save you from a hefty fine.