Born and raised in the San Fernando Valley (CA), I’d always been accustomed to hot summers.  It wasn’t at all unusual to hit the ninety-degree mark in May and be pretty much stuck hovering right around that mark until July, when the triple digits arrived.  And August could be blast furnace hot.  The kind of heat where you don’t even realize you’re sweating because it evaporates so fast.  The kind of heat that, if there’s any wind at all, feels like a hair dryer in your face.

Our house didn’t have any air conditioning.  Instead, we had a big exhaust fan in the bathroom window at one end of the house, and every night, we’d crank that puppy on full blast and open all the bedroom windows at the other end of the house.  It was the only way to get any sleep.  If it wasn’t cool, at least the air was moving.

We could hit 110, even 115 degrees by mid-August and it never seemed to make the news.  But when a heat wave hit New York or Chicago—a “heat wave” in those parts being in the neighborhood of 85 degrees—it made headlines.  I never could understand that.  To us, 85 degrees constituted a fine spring day.

Now I know  better.

Summer in Wisconsin is short, but it can be brutal.  People complain all winter long about the cold, but come July, it’s the heat that makes us fall to pieces.  And it has been hot this week.  Seriously hot.

The official definition of a heat wave in these parts is when it hits 90 degrees for three days straight.  We’ve been in the nineties all week, with heat-index temps hovering around a hundred.

Back in California, hitting ninety meant things were cooling down.  Even a hundred, out there, is pretty normal.  Not so, here.

Everyone says it’s not the heat, it’s the humidity.  But more accurately, it’s the dew point.  Before I moved to Wisconsin, I had never heard of dew point; apparently in California it’s a non-issue.

But it has great significance here.  There are ninety-degree days, and then there are ninety-degree days.  They are not all created equal.  A ninety-degree day in Southern California is a completely different species from a ninety-degree day in Northwestern Wisconsin.  And dew point is what makes the difference.

Dew point, if you’ll excuse a ridiculously oversimplified definition (feel free to google a more complex one), is the temperature at which dew will form.  That is to say, the point at which the air turns to water.  The higher the dew point is in relation to the air temperature, the heavier and thicker the air is, and the heavier and thicker the air is, the harder it is to breathe.  When dew points are high, perspiration can’t evaporate because it has nowhere to go.  The air is already so saturated that if there’s no breeze, you have little choice but to stew, more or less literally, in your own sweat.

It is a purely miserable feeling, and it simply makes you hotter than the same temperature would in the desert.

California, Nevada, Arizona . . those are deserts.  Not a great deal of water around those parts.  But if everyone knows Minnesota is the land of ten thousand lakes, they’re often unaware that Wisconsin can brag of more than a million acres of its own.  That’s a lot of evaporation going on.

As I understand it, places with more water in the ground have more water in the air as well, and thus they also have higher dew points.

A dew point under 60 degrees is pretty livable.  But once it hits 60, it gets pretty sticky.  The dew points here all week have been in the low to mid SEVENTIES.  For people with respiratory issues, dew points in the 70’s (and heaven forbid, the 80’s) can be deadly.  If your dew points are up there, you need to find someplace with central air conditioning and stay there until the heat wave breaks.  That’s no joke.

And if you’re currently suffering triple-digit temperatures in an arid climate, and you can’t understand why all these 90-degree temperatures elsewhere are grabbing all the headlines, you can blame the dew point.  In this kind of saturated air, the human body simply can’t cool itself.

I understand that you’re sick and tired of hearing people tell you how lucky you are that you’ve got dry heat, but believe me—you are.