In the summer, drinking more water comes naturally for a lot of people. After all, there’s nothing like a hot, humid and active day that gets you to reach for an icy cold glass of water!

In the fall and winter, however, have you ever noticed how your need for water isn’t always quite as obvious? Here’s why that happens.

1. Research has shown that our sense of thirst is blunted by up to 40 percent in colder weather.

According to at least one study, there’s a physiological response behind why we don’t exactly feel as thirsty when we’re cold. You know how your hands, feet, nose and even ears feel freezing when the temperature drops? Well, those cold sensations also impact your thirst sensation.

When you’re cold, blood is prevented from flowing freely to the extremities due to the way your blood vessels constrict in colder temperatures. And as a result, your body is tricked into thinking it’s good and hydrated, when in fact it may not be.

2. Greater amounts of coffee to cope with the colder weather can throw your body for a loop.

For a lot of people, the multiple cups of coffee they consume every day is what makes the fall and winter seem just a little more bearable. It’s long been thought that caffeine is a diuretic, but some studies have shown that it doesn’t have the dehydrating effect we thought it did.

In fact, the bigger issues lie with caffeine-induced headaches, jitteriness, anxiety, crashes and insomnia. More caffeine doesn’t leave you significantly dehydrated, but it doesn’t make you healthier either, so balancing it out with more water is always a good idea. If coffee is what gets you through the colder months, consider switching it up from time to time with decaf coffee, caffeine-free herbal tea and most importantly—plain water.

3. Respiratory fluid loss increases in colder weather. 

No matter what time of year it is, we all lose some amount of fluid through respiration. When the temperature drops, however, that’s when we tend to lose more. In fact, respiratory fluid loss increases by up to 5 mL per hour when breathing in cold, dry air. To put that in perspective, normal respiratory fluid loss is about 250 to 350 mL per day.

If you live in any part of the world that has dramatic seasonal changes, then you’ve no doubt been able to see your breath outside in the cold. The breath that you see is actually water vaporizing from your body.

4. Wearing heavier clothing causes your body to lose more water through sweat.

Bulky sweaters and scarves may be in fashion, and they do help with conserving heat, but they also make your body work harder compared to when you’re wearing lighter clothing. More sweat equals more water loss.

5. The colder weather causes sweat to evaporate more quickly.

It’s often hard to tell whether you’re really sweating or not when it’s cold out, because colder and drier air makes sweat evaporate at a faster rate. Athletes and people who engage in physical labor outside in the colder weather need to be especially aware of how much water they are or aren’t drinking since they’re more prone to experiencing cold-induced urine diuresis—a hormonal response that signals the kidneys to pull out excess fluids in order to lower blood pressure, in turn producing more urine.

You may not be thirsty, but it’s important to be mindful of how much water you’re drinking as the colder weather and darker days set in. Your brain and your body will thank you for it!

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