From temperature swings to shifts in humidity, changes in the environment can affect your health in surprising ways. Cold weather: Cold air irritates airways and can trigger asthma in some people. And the dry air dehydrates and cracks your mucus membranes, increasing your vulnerability to viruses and worsening respiratory issues. Cold weather also prompts behavior changes that increase your risk of getting sick. After all, when it’s chilly outside, you’re more likely to hang out inside. And so is everyone else. There are more germs indoors and the ventilation isn’t as good. Cold stress is also a serious concern when temperatures drop below freezing. Warm weather: Hot weather puts added stress on your heart and blood vessels. It also causes dehydration, exhaustion and other complications, like heat stroke. Also, late spring and summer are ideal for spending time outdoors. All that fresh air means you’re less likely to get a respiratory infection. But it also means allergy season is in full swing. And that can make you feel just as gross. Barometric pressure changes: Sudden changes in air pressure can cause a wide range of symptoms, including: Joint stiffness Migraines Sinus problems Shortness of breath Fatigue It can even affect blood pressure and balance, particularly for people with inner ear or certain nervous system disorders. Changing humidity: High humidity puts added stress on your body. When there’s a lot of moisture in the air, it can cause fatigue, joint pain and breathing difficulties, especially if you have chronic health issues. Mold, fungi and allergens thrive in high humidity, too. Meanwhile, low humidity has a drying effect. That can be bad news for your immune system because it can cause systemic inflammation and damage your body’s natural defenses, like your skin and mucous membranes. Interestingly, both high and low humidity can increase your risk of dehydration. So, be sure to drink plenty of water all year long. Precipitation: Warm, wet weather creates an ideal environment for: Mosquitoes Bacteria Fungi Mold Rainy weather also tends to make seasonal allergies worse. Snowy or icy conditions can be just as hazardous: The combo of below-freezing temperatures and wet weather can cause hypothermia if you’re exposed to it for too long and aren’t properly dressed. UV radiation: Sunscreen is essential year-round, but even more so when the UV index is high. Prolonged exposure to ultraviolet (UV) rays can lead to sunburns, hyperpigmentation and increased risk of skin cancer