Dehydration becomes rampantly common from October to February, and while it isn’t as severe as to place it in the same category as seasonal affective disorder (SAD) a.k.a. “winter blues,” it is still a widespread yet preventable condition. Many of the headaches and general fatigue experienced during the winter can be assuaged by drinking more water. This is not to downplay the effects of conditions, such as SAD.

We surprisingly get a chunk of our water from our foods – about 20% of daily water intake, but the other 80% comes directly from consuming beverages. Excluding special hydration treatments such as IV supplements, hydration is dependent and limited to two modes, so it becomes even more imperative that you take te time to assess when you last drank water.

Due to a combination of cold weather and preference to stay indoors, people generally perspire much less. While sweating serves as a good, visible cue to replenish lost water and minerals, there’s an inappropriate dependence on damp pits as the gauge of hydration. This dependence turns into a real problem during winter because of two reasons: diminished thirst response and cold-induced diuresis.

In the cold, the human body's thirst response is significantly diminished -- "by up to 40 percent even when dehydrated" (DripDrop). Or in other words, in the cold, your body misinforms you about how hydrated or dehydrated you are.

This is because both body temperature and thirst responses are controlled by the hypothalamus. So when the body is exposed to gelid temperatures, the hypothalamus automatically drops many of its other responsibilities (e.g. fatigue, hunger, sleep and circadian rhythms) to focus on maintaining the core body temperature. Blood vessels constrict, cutting off much of the blood flow to the extremities and thus pulling the rest of the blood supply to the core ("peripheral vasoconstriction"). Makes sense, right? Like, who cares if you're thirsty if all of your organs are frozen? This disregard by the hypothalamus, however, can become life-threatening by reason number two.

When the blood is drawn from the extremities and to the body's organs, the body is tricked into thinking it is properly hydrated due to decreased "extracellular thirst." Extracellular thirst, or hypovolemia, is the thirst caused by the decrease in the volume of blood plasma, whereas intracellular thirst is determined by osmolyte concentration.

Imagine a round balloon half-filled with water. When your body feels cold, it triggers peripheral vasoconstriction, squeezing all of the air out of the balloon without removing any water. The overall volume of the balloon has diminished, so the water content which was 50% before is now nearly 100%. Through vasoconstriction, your body has satiated its extracellular thirst.

This, however, is a temporary solution as the body's blood volume needs to stay within a small range. The problem then becomes a race against time without knowing you're in the race.

Vasoconstriction of any kind is a mechanical alteration that creates a smaller volume for the blood to fill. This works as a temporary buff in cases of blood loss, but it is also a contributing cause of cold-induced diuresis.

As the arterial walls begin to tighten, blood pressure naturally increases ("mean arterial pressure"). This jump in mean arterial pressure prompts the kidneys to relieve the pressure by excreting "superfluous" fluids. Within an hour of experiencing mild hypothermia, you have pissed away your hydration without realizing it.

There are some good ways to check hydration levels, and one prime example is to look at the color of your urine. The rule of thumb is that if it's yellow, you're on the verge of dehydration. If it's brownish-yellow, you are dehydrated.

A quicker way to check is to see how dry your lips are. Run a finger over the lips; if it's hard or has ridges, you are likely to be dehydrated. Dried lips are directly correlated to hydration, but lip balm use can feign hydrated lips which may reduce the validity of this check. Inversely, the dry, winter air can crack the plumpest lips of a hydrated person.

Open and straighten your non-dominant hand, palm facing down. With the dominant hand, lightly pinch the wrinkly fold on a joint of any finger. Then release the pinch. If that fold goes back to its natural shape right away, you're hydrated. If the fold slowly reverts or stays in the pinched shape, you are dehydrated and should drink something very soon.

Dehydration is already difficult to notice throughout the year, especially in the air-conditioned settings where we go hours without considering a sip, so take care of your well-being at a time when even your body is working against you. Your body becomes numb to your needs even more because of instinctual responses to cold stimuli.

So fill up your cute, lil S'well bottle, down that bottle, and you will feel like Christmas morning all throughout the cold, winter months (and through finals).

Tl;dr: your body is lying to you.

Note: This article makes two assumptions: 1) Reader lives in the northern hemisphere and 2) Reader has ready access to potable water. If you live in the southern hemisphere, the corresponding months may be April to August.