It’s very frequent to get sick when the temperatures are low. And we know that while it’s not the actual cold that makes you sick, it makes you prone to it by weakening your immune system and thus making it easier for viruses and bacteria to overcome your defenses.
But what about the opposite?
Some years ago, a friend of mine who was used to the cold North European weather went to Southern France for an internship and spent the first week in bed with a fever and a sore throat. The doctor’s diagnosis was “un rhume de chaleur” (“a cold from the heat”).
On the face of it, it makes sense. Like the cold, a heat wave probably weakens your immune system. But on the other hand, aren’t high temperatures less than ideal for viruses and bacteria to thrive?
So, is there such a thing as a “un rhume de chaleur” ? Just to be clear: I’m not talking about getting a cold while going from a place with air conditioning to the hot open air and vice versa but getting a cold where only the heat is enough to make you an easier prey for microbes.
This is not settled science. It has never been proven that exposure to cold temperatures weakens your immune system. That’s just one possible explanation. A competing explanation is that, during cold temperatures, people spend more time indoors, in closer proximity to other humans, which makes it easier for the virus to jump from one human to another. Another explanation is that during cold temperatures you touch your nose more often, which greatly increases your risk of contracting a cold if the virus is on your hand right after you touched something that an infected person just touched.
It’s certainly possible that there could be similar mechanisms which operate during extremely hot weather. For example, if you live in a place where there’s lots of indoor air conditioning, then people may spend more time indoors when it’s hot, and the proximity could increase the transmission rates of airborne viruses. Or if the hot weather corresponds with other activities like vacation travel then you could be coming into contact with larger numbers of people than usual.
I remember walking into an office in Houston during the baking summer months. The receptionist was sneezing and had a heavy cold. It seemed quite chilly inside and she was wearing warm clothing.
I guessed it was the badly maintained air conditioning. Nothing like sitting in a blast of chilled air, full of recirculated microbes for picking up a cold.
