12 Science-Backed Answers to the Question: Does Cold Weather Make You Sick?

5. Virus Stability in Cold, Dry Conditions

Some respiratory viruses are more stable in cold, dry environments. Laboratory work shows that influenza and certain coronaviruses may remain infectious longer on surfaces or in the air when humidity is low and temperatures are cooler. That increased stability can raise the chance that a nearby exposure leads to infection. However, lab conditions don’t always match real life, and many variables influence transmission. The practical takeaway is to use layered protections rather than relying on a single measure. Combine vaccination where appropriate with good ventilation, routine hand hygiene, and sensible surface cleaning for high-touch items. These combined actions reduce the likelihood that a lingering particle will find a way into your airway. In other words, layering simple precautions gives you greater overall protection than any single tactic on its own.

6. Reduced Sunlight, Vitamin D, and Immunity

Shorter days and less time outdoors can lower many people’s vitamin D levels during winter. Because vitamin D plays a role in immune regulation, low levels are linked in some studies to higher rates of respiratory infections. This link doesn’t mean that boosting vitamin D alone will fully prevent colds, but it is a modifiable factor worth attention. If you’re concerned about deficiency, check with your healthcare provider about testing and safe supplementation. Food choices—like fatty fish and fortified dairy or plant-based milks—can help maintain levels, and brief, safe sun exposure when possible supports natural production. For older adults or people with limited sun exposure, supplements under medical guidance are a practical strategy. The key is balance: use sunlight, diet, and targeted supplementation as part of a broader approach to supporting immunity rather than treating any one measure as a cure-all.