So often, especially this time of year, you hear us say, "A lake breeze will cool us down." Or "Cooler by the lake."  Sometimes you will hear us say, "A thunderstorm can't be ruled out along the lake breeze front."  So what causes this?

It all comes down to the specific heat of a substance.  Specific heat is defined as, the heat required to raise the temperature of the unit mass of a given substance by a given amount (usually one degree). 

Water has a high specific heat.  The specific heat of water is 1 calorie/gram °C = 4.186 joule/gram °C which is higher than any other common substance. As a result, water plays a very important role in temperature regulation.

Land has a much lower specific heat.  Ashphalt even lower.  That is why it's not easy walking barefoot across a driveway or even a deck as wood has a low specific heat as well.

So when the sun comes up, it heats up the land rather quickly, but on a daily basis the water temperature doesn't change much.  So now we have the surface of the land heating up into the 70s and 80s, while the water (as well as the air immediately above it) this time of year is in the 40s and 50s. 

The atmosphere is heated from below.  So the land heats the air above it quickly to the 70s, 80s, 90s.  While the air above the water is closer to the 40s and 50s.  This is what sets up a micro (small scale) circulation. 

As the air rises above the land, that void needs to be filled in.  Because just like trying to dig a hole in water, it's impossible to dig a hole in the air.  So as this hot air rises, air from nearby rushes in to fill the void left at the surface.  Since the air filling that void was over the cold water, you can hav e the temperature suddenly drop 10, 20, even 30 degrees.  I witnessed this on Memorial Day.  It was pushing 90 and very uncomfortable with a light south wind.  5 minutes later the breeze suddenly picked up out of the north and the temperature dropped some 20 degrees!   

This is what makes our weather so special.  So many small scale influences on our climate.   

So whenever you are planning to golf, picnic, or just hange out by the lakes this time of year, grab a jacket even though it may be in the 80s and 90s at your house.