When temperatures drop, does reaching for a glass or bottle of water fall to the bottom of your to-do list? After all, it’s not like you’re sweating in the summer sun or feeling thirsty due to outdoor exercise. But here’s what you might not realize: winter dehydration is a real and underestimated health risk that affects everything from your immune function to mental clarity.

Hidden ways winter dehydrates your body

Cold weather creates a perfect storm for dehydration. According to Julie Metos, a registered dietitian at the University of Utah, the body continues to lose water through perspiration and breathing—even though those losses are far less noticeable in winter.

Several factors contribute to winter dehydration. The dry air—both outdoors and from indoor heating systems—strips moisture from your body with every breath. Research conducted by Robert Kenefick, PhD, who is currently a professor and chair of the Department of Biomedical and Nutritional Sciences, Zuckerberg College of Health Sciences, at the University of Massachusetts-Lowell, found that people lose significant amounts of water vapor simply through respiration in cold, dry conditions. The research noted that wearing heavy layers increases perspiration, although the sweat evaporates quickly in dry air, so you don’t notice it like you do in summer’s heat. And cold temperatures cause blood vessels to constrict, reducing the body’s natural thirst response. Kenefick’s study, published in Medicine & Science in Sports & Exercise, found that cold exposure can reduce thirst sensation by up to 40%.

Adding to the problem, when fighting a winter cold or flu, your body’s water needs increase. A slight fever raises fluid requirements, and adequate hydration can help thin the mucus in your nasal passages and lungs.

Why you might not realize you’re dehydrated

The warning signs of dehydration can be subtle or entirely absent during colder months. Because you don’t feel as thirsty in winter, you may drink fewer fluids without even noticing. That’s problematic because by the time you actually feel thirsty, you’re already a little dehydrated!

According to the hydration expert Lawrence E. Armstrong, PhD, even a 1%-2% loss in body weight from fluid loss can affect mood, energy levels, and mental awareness—yet many people don’t connect those symptoms to dehydration. You might chalk up your fatigue to shorter daylight hours or blame foggy thinking on stress—never suspecting that insufficient water intake is the real culprit.

Older adults face particular risks, often intentionally drinking less to avoid frequent trips to the restroom—a habit that leads to serious dehydration when combined with winter’s reduced thirst signals.

A simple way to test your hydration needs

One of the easiest ways to monitor your hydration status is by checking the color of your urine. According to the Cleveland Clinic, “Urine that falls in the pale yellow category signals that you’re healthy and hydrated… Darker urine is your body talking to you. What’s it saying? Basically, drink some water… The darker hue is a sign of mild dehydration.”

Water is best for healthy hydration

The newly released 2025-2030 Dietary Guidelines for Americans, published by the U.S. Departments of Agriculture (USDA) and Health and Human Services (HHS), reinforces water’s essential role in healthy hydration. Its recommendation is clearly stated: “Hydration is a key factor in overall health. Choose water (still or sparkling) and unsweetened beverages.”

This federal guidance underscores an important point—when it comes to healthy hydration, water should be your first choice over sugary beverages, which add unnecessary calories and increase the risk of chronic diseases like Type 2 diabetes.

Practical tips for staying hydrated this winter

Maintaining proper hydration during winter requires intentional effort. Here are some strategies to help you stay on track:

• Keep a bottle of water with you—at your desk, in your car, and by your bedside—and sip throughout the day.
• If you drink plenty of water during summer, maintain that habit during colder months.
• Set regular reminders to take water breaks, especially if you don’t naturally feel thirsty.
• For those who find cold water unappealing in winter, herbal teas and warm water with lemon count toward your daily fluid intake.

And remember—whether from the tap, filtered, or bottled—water remains the healthiest choice for keeping your body properly hydrated all winter long.