In short, the answer is a resounding, “Yes”! Your nose knows that smells seem stronger in wet, humid weather.

The hypothesis that humidity causes things to stink more has been tested by scientists and the results published in a scholarly journal.

The present study is aimed at investigating the question whether olfactory function changes in relation to barometric pressure and humidity…[the result] In conclusion, environmental conditions modulate the sense of smell, and may, consecutively, influence results from olfactory tests.”1

So all of you who have noticed that many things seems to smell worse during the summer are 100% correct!

Here’s the How and Why

Humidity is a term we use to describe the amount of water that has vaporized and is being held in the air. A meteorologist would use the term ‘relative humidity’ to compare the amount of water currently in the air, versus the amount of water the air could hold. In turn the amount of water the air is capable of holding varies directly with the temperature. Very cold air can only hold a little bit of water. But when it warms up outside, the air can hold more humidity. This is why an air conditioner needs a drain. When it cools warm moist air, that air can no longer hold as much water so the moisture condenses into droplets that then need to be drained away. You might be surprised how much water drains away like this! That drain is important because if it becomes blocked and the water cannot drain, it may very well spill over the container and puddle somewhere becoming a source of moisture that then allows mold, mildew and/or fungus’ to grow wherever that puddle is.

Another sort of smell is caused by the acidity of rain. Because of chemicals in the atmosphere, rainwater tends to be somewhat acidic, especially in urban environments. When it comes in contact with organic debris or chemicals on the ground, it can cause some particularly aromatic reactions. It breaks apart soil and releases minerals trapped inside, and it reacts with chemicals, such as gasoline, giving them a stronger smell. These reactions generally produce more unpleasant smells than bacteria spores, which is why the after-the-rain smell isn’t always a good one.”

Fortunately, it is not only bad smells that are more pronounced after the rain. Think of that walk you took after the rain when you noticed all those wonderful smells! Ummmm! Freshly mown grass! This is the pleasant aspect of the moisture / smell relationship.

Wet Dog Smell

Yep – you sorta knew this already, but your dog is, “crawling with musk-emitting microorganisms”. The real source of that stink is coming from the “excrement of bacteria and yeasts living in his fur”. Not to mention the excreta of any ticks and fleas that may inhabit your best friend.3

Household Odors

Our homes are not exempt from moisture-enhanced odors either. Many of you with basements know that during the summer months, when it has been raining that the basement becomes musty or moldy smelling. The increased moisture content of the air not only allows mold, mildew, or fungus to grow, but those odors become extra smelly as well. A clear double whammy!  And that kitty litter box – yes indeedy!  It is more smelly during the summer months -just like you always suspected!

What To Do?

Run the air conditioner if you can afford it. Because cold air cannot hold as much moisture and warm air, when you run the A/C, it removes excess moisture which helps reduce odors and slows down the growth of mold and etc. If you still get that musty smell, it may help to put some Nok-Out or SNiPER into a vaporizer and ‘dose’ your basement periodically. See and


  1. – “Changes of pressure and humidity affect olfactory function”; Authors: Michael Kuehn, Heiko Welsch, Thomas Zahnert, Thomas Hummel
  2. – “What causes the smell after rain?”
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