Can Cold Weather Make You Sick?

The odds of catching the common cold or influenza are highest during the fall and winter. However, the weather itself cannot cause either of these viral illness. It can, however, set the stage for certain factors that decrease your immunity and increase opportunities to catch a cold or the flu.

Cold, Dry Air

There is some evidence to suggest that viruses spread more easily through cold, dry air. Temperature and humidity, therefore, may affect your risk of contracting a virus.

When it is cold outside, the air is drier both outdoors and inside (due to heating), drying out mucous membranes and making it easier for germs to take hold.

The nose is an ideal host for many viruses due to its cooler temperature. The typically core body temperature is 98.6 degrees F, but the nasal cavity temperature is lower at 91.4 degrees F. Research suggests that rhinoviruses do not replicate efficiently at body temperature, but the cooler temperature in the nose may make it an ideal breeding ground for viruses.

One study suggests colder temperatures on their own do not increase the spread of colds and flu, but temperature and humidity fluctuations do. Researchers cross-referenced confirmed cases of rhinovirus with weather data over a set period of time and discovered that decreases in either temperature or humidity over a three-day period increased the risk of rhinovirus infections. 

The study, which involved 892 men in the Finnish military, also suggests that breathing cold air may contribute to the spread of infection into the lungs. This is based on earlier research that found lung temperature can be lowered by inhaling cold air. However, researchers also noted that the risk of rhinovirus infection is reduced at subfreezing temperatures and higher humidity.

Warmer air does not necessarily kill viruses, either, as is evidenced by the spread of colds and flu in tropical areas where it does not get cold. Cold and flu cases are more prevalent in tropical climates during the rainy season. This is likely due to people spending more time indoors when it's raining, putting them in closer contact with others than during the dry season.

Cold and flu symptoms are caused by more than 200 different viruses that spread from person to person. The influenza virus responsible for the seasonal flu spreads across the United States from October to April. Rhinovirus has more than 150 different circulating strains at any given time and accounts for more than half of all colds each year. Various strains of coronavirus, enterovirus, parainfluenza, and respiratory syncytial virus (RSV) can cause different degrees of congestion, fever, cough, and body aches. 

Reduced Immune Function

People may also be more prone to catching a cold or flu in the winter due to lower immunity. Fewer daylight hours and less time spend outside mean less exposure to sunlight, which the body uses to make vitamin D.

Vitamin D plays a critical role in the immune system helping to keep you healthy. Vitamin D deficiency is linked to an increased risk of infections. However, there is insufficient evidence to support the use of high-dose vitamin D for the prevention of viral upper respiratory infections.

People also tend to be less active in cold weather. While it is not clear exactly if or how exercise increases your immunity to certain illnesses, and no solid evidence, there are several theories, about exercise, such as:

  • It improves circulation, allowing white blood cells to detect and fight an infection faster.
  • It increases body temperature during and right after a workout, which may work like a fever to prevent bacteria from growing.
  • It may help to flush bacteria from the lungs and airways, reducing your chances of getting sick.
  • It lowers levels of stress hormones, which may protect against illness. 

Close Contact

Viruses rely on the cells of other organisms to live and replicate. They are transmitted from host to host when infected respiratory secretions make their way into the mucous membranes of a healthy person. This can occur from direct person-to-person contact, by inhaling small droplets in the air, or by touching something that has the virus on it and then touching your mouth, nose, or eyes. 

It logically follows, then, that the closer you are to people and the more you share a space, the more likely transmission is. In the winter, many people tend to take their outdoor activities in: school recess is held in a gym, rather than outside; people walk around crowded shopping centers rather than on a track. This close contact during colder months increases the likelihood of passing germs.

Protection From Cold and Flu

The most important thing to remember during cold and flu season is to protect yourself against these germs when you are around other people.

Be sure to wash your hands often or use an alcohol-hased hand sanitizer if you can't get to a sink. Try to avoid touching your face as much as possible, since that is how most respiratory germs enter the body. 

You can also protect yourself against illness by getting your yearly flu vaccine, avoiding people who you know are sick, and taking care of your body by eating nutritious foods, exercising regularly, and getting enough sleep at night.

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