Does Cold Air Kill Germs? What About Heat?

Here's a common question: Can a cold or hot air kill germs It's that time of year again when your nose is dripping out of control. While you're having your sneezing frenzy, ever wonder why does the flu spread in the winter? Shouldn't the freezing cold temperature kill the germs and end the flu epidemic? Can heat do the job if cold can't kill bacteria and viruses? Don't worry, as we have all the answers here. Any questions involving temperature, germs, and weather will be addressed below.


Here are some scary stats about the flu from CDC5% to 20% of the U.S. population gets the flu yearly. That’s 9.3 million to 49 million illness cases since 2010. Flu results in 31.4 million outpatient visits and more than 200,000 hospitalizations annually. 58% of the deaths occurred in adults aged above 65. The flu costs an estimated $10.4 billion annually in medical bills. It also affects employees to miss around $17 million of a workday. In 2017-2018, the flu vaccine was rated at 40% effectiveness and prevented 5.3 million illnesses.

Does Cold Air Kill Germs?

Cold air and snow do not kill germs, bacteria, or viruses. Most germs will stay dormant in freezing temperatures until the membranes inside break, dry off, and die (under extreme weather). Germs like the flu virus are more cold-resistance and can thrive in cold weather during the winter. Another common problem is bacteria and viruses may have already found their way into a host’s warm body. Our human body will provide the right temperature and nutrients for the germs, shielding them from the outside cold weather.

Do Germs Spread Faster In Cold Weather?

Yes, cold weather actually helps germs, bacteria, and viruses spread faster. According to the National Institutes of Health, cold air protects the virus by forming a hard outer layer of envelope gel. The protected virus will stay longer in the air, thereby increasing the risk of transmission or a person inhaling it. Dry air with very little moisture is another common theme in cold weather. When the humidity level is low, air droplets are small and light, making it easier for viruses to spread airborne. Conversely, droplets are larger and heavier in humid conditions, making them fall faster.

Most germs will slow down, stay dormant, and even die if the weather drops to a freezing temperature. However, some germs and viruses will survive the freezing weather and will begin multiplying when thawed due to the increased temperature. For example, Influenza (flu) or Rhinovirus (cold) will thrive and multiply in cold temperatures.

Cold weather on its own will not make us sick. However, it can dry out our nasal passages and mucous membranes, making them more vulnerable to virus infection. A good indication of germs transmitting rapidly in cold weather is people tend to catch a cold or seasonal flu during the winter months.

Does Heat Kill Germs?

According to WHO, Germs, bacteria, and viruses can be killed through heat at 140º F or higher. Heat will break down the molecule structure of germs, thus disabling their functionality. The higher the temperature, the faster germs will be killed. A hot bath or shower is not hot enough to kill germs, and the dampness will help mold growth. UV-light or sterilizer will be a better choice for eliminating pathogens via ultraviolet light by damaging their DNA. There are a few exceptions, though. Germs like hyperthermophilic bacteria can adapt to survive in very hot temperatures up to 250°F degrees. Fortunately, those germs are rare and few that you should not be alarmed about.

Do Germs Spread Faster In Hot Weather?

Hot weather are more likely to kill or slow down most germs, bacteria, and viruses from spreading. When exposed to high heat energy, the outer protective capsule of the viruses will melt and expose the fragile body. It causes the protein in the germs and viruses to denature or lose its functional form. Respiratory droplet formations are also why germs spread slower in hot air. As hot weather can be extremely humid e.g. in the summer, droplets are larger and heavier, making it hard for the germs to transmit. Airborne germs and viruses will also drop faster due to extra weight. Keep in mind that some viruses can adapt to warm temperatures better than others, so proper hygiene is still the safest solution.

What Temperature Kills Germs In The House

Most germs will die from 165 degrees F to 250 degrees F (121°C) within a couple of minutes. That’s the recommended temperature from food scientists to heat up meat, fish, and pork before serving. Some viruses can be killed at 140 degrees F temperatures (hot water). For dry heat sterilization, switch the temperature to 320 degrees F (160°C) for 2 hours or 338 degrees F (170°C) for 1 hour.

Take note that not every heat can kill germs. Also, boiled water is much safer to consume than hot water. The more prolonged the germs are under extreme temperatures, the faster and more germs will die.

How To Protect Yourself From Germs And Viruses

So no matter how hot, cold, humid, or dry the air is, germs will always be around. Remember, germs, viruses, and bacteria will react differently to cold or hot temperatures. The pathogens will also have different life expectancies to be transmissible when living on other surfaces. Most germ flu will live up to 3 days or 72 hours on hard surfaces like stainless steel and plastic. The same germ flu will only live up to 24 hours on paper or cardboard. On fabric surfaces like clothes, pillowcases, and bedding, flu viruses can live 8 to 12 hours, depending on temperature and humidity. For example, germs in a wet towel will survive longer than in a dry towel.

Even though most germs are bad for us, studies show that some exposure can help strengthen our immune system. That doesn’t mean we should openly expose ourselves to bacteria and viruses. Preventive measures and good hygiene is the best way to protect us from falling sick to germs.

For contaminated clothes or upholstery, a hot temperature is preferred over cold. You can kill germs by washing them in high heat temperatures around 140°F to 150°F together with detergent. After that, dry it with a tumble dryer and high heat at around 150°F to completely disinfect bacteria, fungus and prevent further growth.

For dishes, you can wash and rinse them with hot or cold water. The best way is to use a dishwasher that can output hot temperatures to sterilize the bacteria. You can still clean and rinse the dishes through hand wash but preferably with hot water at 113°F.

For food-related bacteria like Legionella, cooking will do the trick, as germs can be killed by boiling water, pasteurizing, or baking with an oven. Most canned foods are prepared at high temperatures to kill all germs. That said, you should always keep food refrigerated as bacteria thrive between 40º F to 140º F. There are extremophile microorganisms that can survive in extreme temperatures and conditions. Thankfully, those are the rare few we don’t encounter very often.

Ultimately, practicing good hygiene is the key to avoiding infection. The best way to protect yourself from germs, bacteria, and viruses is to wash your hands frequently with soap and water for at least 20 seconds, especially after using the restroom, cooking, changing diapers, touching animals, and grocery shopping. It doesn’t matter if it is cold or hot water you are washing your hands with, as long as it can get the dirt and germs off your hand. Dry them thoroughly with a cloth or paper towel. You can also clean your hand with alcohol-based hand sanitizer when you’re outside. By keeping your hands clean, you reduce the risk of germs being transferred to your eyes, mouth, and nose via touching.

From the doctor’s perspective, the body’s immune system tends to wear down in cold weather as we run low on vitamin D (sunlight). Vitamin D is paramount for our immune system function to prevent a cold. Our blood vessels will thicken when we breathe in cold air to help retain our body heat. It causes the white blood cells to ignore the harmful viruses, and we end up with bad flu like influenza.

To recap, germs love indoors as it is the best place for them to flourish. So to prevent the flu from spreading too much love, here are tips that prevent you from falling sick to the viral flu.

  1. Get a humidifier – A humidifier can resolve very dry air conditions and mucus membranes by dispersing water vapor. By maintaining the room humidity level between 30 to 50 percent, our nasal passage will be kept moist and form protective barriers against germs.
  2. Take Vitamin D supplements – The days are short during the winter, and the lack of sunlight will contribute to the low levels of Vitamin D. Vitamin D help boost our body’s immune system against germs, viruses, and respiratory infections. Take 600 to 2,000 IU of vitamin D3 daily to prevent catching a cold and flu up to 70 percent.
  3. Get some fresh air – Especially during the cold winter seasons, as viruses often spread airborne from person to person carrying the germs. Most people will spend their time cooped up in an enclosed area. Whenever possible, go for a long walk instead of staying home the whole day.
  4. Get an air purifier with UV light – Germs can stay suspended in the air for days until it is inhaled or ingested. An air purifier will trap and eliminate airborne bacteria and viruses 24 hours a day without fail.
  5. Stop touching yourself – Viruses and germs often pass from hand to mouth. Avoid touching your face, nose, rubbing your eyes, biting your nails, and wiping your mouth. Sanitize your hand as frequently as possible. Also, keep social distancing with minimal contact from outsiders. Physical contact is the leading cause of virus spread.
  6. Disinfect everyday items – Any surface objects will have the risk of germs contaminated through indirect contact transmission. Disinfect items you touch daily, like a doorknob, remote controls, keyboards, handles, etc. There is no shortage of disinfectants in the market that are specifically designed to kill harmful bacteria, viruses, and germs. Sanitizers can quickly remove germs from soap, while disinfectants kill germs permanently.
  7. Exercise regularly – At least 3 times a day for 20 minutes. It can improve the body immune system and upper respiratory tract from infections.
  8. A good night sleep – Between 6-8 hours without any interruption. A person with consistent quality sleep is 28% less likely to catch a cold.
  9. Eat protein-rich foods – For example, milk, eggs, fish, and greek yogurt. Yogurt is our favorite as it contains a strain of probiotics that will boost our body’s defense against viruses.
  10. Take flu shots – Some vaccines can be taken annually to protect against infections like influenza viruses.
  11. Don’t smoke or hang around with smokers – Smoking increases your chance of respiratory infections. You will be more vulnerable to seasonal colds, influenza, or H1N1 (swine flu).

Does Fresh Air Kill Germs?

Research shows fresh outdoor air is a natural disinfectant that will kill germs and bacteria. That said, the study clearly identifies sunlight's contribution as a germicidal to kill the flu viruses. Enclosed areas like the bedroom and basement tend to have poor air quality as the air is filled with germs passed on from various sources. By opening windows to improve room ventilation, you are airing out the stagnant air and letting fresh air in that has been disinfected by the sun.

Why Do We Get Colds In Winter?

The reason why we always get colds and flu in winter is because of the lack of outdoor activities. Cold weather weakens the body's defenses against infections. Rather than out in the open air, we will spend more time indoors with poor air circulation, surrounded by people that may be sick. For instance, shopping malls, cinemas, cafes, and train stations will be packed with people carrying germs. Germs are often passed from person to person through cough, sneezing, or simple gestures like shaking hands and hugging. You will more likely catch a cold through direct contact than an airborne virus.

Another reason colds and flu are more prevalent in winter is the lack of natural sunlight. Sunshine can kill bacteria and viruses, according to many studies. As the density of airborne germs is less, our exposure rate to the microorganisms would also decrease. Bacteria and viruses live longer indoors during winter as the air is less humid than outside.

[UPDATE] Many readers that landed on this page are actually seeking more information on Coronavirus disease (COVID-19). Here are the verified facts according to World Health Organization (WHO).

  • The coronavirus disease is caused by a virus in a family called Coronaviridae, not bacteria.
  • Taking a hot shower does not prevent you from catching COVID-19 disease. Normal body temperature will be around 97°F (36.1°C) to 99°F (37°C) regardless of a bath or shower.
  • Cold weather and snow do not kill the coronavirus or any other diseases. External temperature or weather does not affect our normal body temperature.
  • You can still catch COVID-19 in hot weather. Exposure to the sun with temperatures higher than 77°F (25°C) does not prevent coronavirus disease.
  • COVID-19 virus can also be transmitted in countries with hot and humid climates like Thailand, Malaysia, and Indonesia.
  • Ultraviolet light should not be used to disinfect hands or other body parts, as UV radiation can cause skin irritation and damage eyes when pointed directly.
  • Hand dryers are ineffective in killing the coronavirus even at the highest setting.

For the latest updates on COVID-19, please go to World Health Organization (WHO) website.

Max Fernandez

A loving father and a dedicated reviewer for airfuji.com with more than 1000 air purifiers under his belt. Max Fernandez is also one of the million patients currently suffering from asthma. Feel free to nudge him if you have any questions.
How Can I Help You Today?

I need air purifier that is to deal with for to be placed in the for with