If you’ve ever stepped outside and sensed a storm brewing, it’s not because you can see the future. You might just have a keen sense of smell.
And if you’ve ever been outside after a storm and declared that rain fell, you’re on the right track there too. That’s because a rainstorm can produce two distinct smells: one before and one after.
The idea that a smell in the air can give away incoming rain is one of many that get passed around whenever a storm rolls across Wisconsin. Here’s what to know about that and other weather theories.
What do I smell before a rainstorm?
Before rain starts to fall, there’s a chance you might notice a smell that the Farmer’s Almanac describes as “slightly metallic.” That’s the smell of ozone, the molecule formed from three hydrogen atoms, one more than oxygen.
During thunderstorms, lightning can zap the air and turn oxygen to ozone, which then gets whisked away by the wind. Since the wind is blowing in the same direction the storm is moving, you might smell ozone before severe weather comes your way.
Ozone also moves from higher altitudes to surface level prior to a storm because of downdrafts from the wind.
What do I smell after a rainstorm?
Rain itself has a smell too, and it even has its own name: petrichor. When droplets of rain strike the ground and soil, small particles get kicked up into the air. Oils build up in rocks, leaves and other natural surfaces during spells of dry weather and the particles – some of which are known as geosmin – are released once they’re hit by rain.
Humans have a high sensitivity to geosmin. Some people have been studied to detect it at a concentration of five parts per trillion.
Other weather questions answered
Do cows lie down before a rainstorm? Depends who you ask. Some sources say yes and others say no, but there isn’t any peer-reviewed research on the phenomenon. Jennifer Van Os, faculty associate director at UW-Madison’s Dairy Innovation Hub, said dairy cows spend roughly half of the day lying down, and will sometimes stand up and lie down more frequently for heat regulation.
Van Os said studies have shown cows respond to current weather conditions by facing away from the direction rain is blowing and bowing their heads.
Does a 40% chance of rain mean it will cover 40% of the area? Not exactly. There are several misinterpretations of what a chance of precipitation means. Some say an 80% chance of precipitation means it will rain for 80% of the day. Others say it will cover 80% of the area.
But, according to the National Weather Service and The Weather Channel, the percentage is calculated based on two factors with some math involved. It’s the meteorologist’s confidence that rain will fall multiplied by the percentage of the area they would expect it to cover. When put together, those two create the probability that 0.01 inches of rain will fall within a specific spot on a map. That probability does not account for timing, pattern, intensity or an exact location within a zone.
Can lightning strike in the same place twice? Yes, it can. And according to the National Oceanic and Atmospheric Administration, it happens quite often, especially to a tall and isolated target. The Empire State Building gets struck by lightning about 25 times per year.
Can tornadoes occur in cities? Yes, but it doesn’t happen often because urban areas make up only 3% of land in the United States. However, that’s the only reason – cities themselves are no less susceptible to tornadoes than any other area. In fact, an EF-3 tornado roared through the Nashville area for 60 miles in 2020 and caused $1 billion in damage.
Lance Schulteis can be reached at LSchulteis@usatodayco.com.
This article originally appeared on Milwaukee Journal Sentinel: When storms roll through Wisconsin, here’s why rain has a smell
Reporting by Lance Schulteis, Milwaukee Journal Sentinel / Milwaukee Journal Sentinel
USA TODAY Network via Reuters Connect
By Lance Schulteis, Milwaukee Journal Sentinel | USA TODAY Network
