Your body is a complicated network of systems that was built by thousands of years of evolution. Usually, it’s pretty good at its job, but sometimes it can be tricked. When it’s cloudy outside, your body’s natural “It’s dark outside, so we should go to sleep” mechanism clicks on and floods your body with the very chemicals you’d probably like to avoid if you’re trying to get work done and stay vertical. That particular chemical is called melatonin, and it’s one of the biggest ways your body regulates your sleep schedule. When it’s dark outside, the melatonin builds up in your brain, but the daylight breaks it down. When cloudy or short days prevent it from breaking down, you’re getting played by your own body. What an embarrassment.

The other chemical that regulates your alertness is adenosine. If you remember your high school biology, you’ll remember adenosine from ATP, or the energy source for muscle movement. Well, when you’re active, that adenosine builds up and tips your body off to the idea that it’s time for bed. You can trick your body into letting you stay up later by drinking caffeine, but sooner or later you’ll have to go to sleep.

Good luck staying awake this winter!