Heat Islands: Urban areas hotter than rural ones?

RICHMOND, VA (WWBT) - Every day we receive emails asking questions about the weather.  But one caught my eye.  It's from "Milton" who asked whether there is a connection between where rain falls and larger cites.

Whether you're watching First Warning Doppler radar on television or looking at your NBC12 Weather app for a mobile device, sometimes it does look like the rain is going right around downtown Richmond.  While that doesn't always happen, cities do have an impact on warm season thunderstorms.

That's because those storms are fueled by heat.  But our heat isn't evenly distributed, because of what's called the "heat island effect."

It means urban areas tend to be hotter than rural communities thanks to more pavement, buildings, and concrete.   So on a hot summer day, downtown Richmond will likely be hotter than rural Powhatan.

And that causes the air in cities to heat up more quickly, and then rise more vigorously than it would in the absence of the heat island.  That can enhance thunderstorm formation.

Usually winds 30,000 feet above the surface in Virginia blow from west to east.   So any thunderstorm that develops here then moves east to eastern Henrico and Charles City County.

Think of it like dropping food coloring into a stream of water.  The water will take the coloring in the direction it's flowing.  There's still coloring where it was initially dropped, but a lot of is carried downstream.

To put this simply, places immediately to the east of downtown Richmond have a higher potential of getting rain on a hot and humid summer day than the rest of us.

This isn't an exact science just yet, but studies have shown this trend occurring around large urban areas in the United States.

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