Metro Detroit weather forecast: A brief break before humidity comes roaring back this weekend

Near-record temps expected Father's Day weekend

By Paul Gross - Meteorologist

A view of Detroit, Michigan, on June 13, 2018. (WDIV)

DETROIT - A cold front swept across the area with just a few showers…most of us didn’t get one…but more importantly, a sharp drop in humidity that you could actually feel if you were outside all afternoon.

Enjoy it while it lasts, because an even steamier air mass has its sights set on us.

But first, Wednesday night will feature absolutely perfect sleeping weather, with rapidly diminishing wind. Clear skies, a very light west wind, and that aforementioned dry air will allow temperatures to drop into the mid to upper 50s (14 degrees Celsius) in most areas outside of Detroit’s Urban Heat Island, where temps will hold near 60 degrees (16 degrees Celsius).

Thursday will be a perfect summer day, with wall-to-wall sunshine, and a light breeze from the northwest, with highs in the mid 80s (29 degrees Celsius). Most importantly, humidity will be much lower, making it a much more comfortable mid 80s.

Thursday’s sunrise is at 5:56 a.m., and Thursday’s sunset is at 9:11 p.m.

Clear skies again Thursday night, with lows near 60 degrees (15 to 16 degrees Celsius).  It’ll be a beautiful evening for the festival meal, Eid al-Fitr, which celebrates the end of the holy month of Ramadan. Many Muslims in our community will gather at friends and relatives homes, and the weather couldn’t be better! We hope you had a meaningful month of observance.

At this point, we need to pause to talk about the dewpoint temperature which, even if you don’t care about it at this moment, we guarantee that you will by this weekend. We talk about dewpoint on the air a lot because, frankly, it’s very important.  Here’s a quick explanation: dewpoint is the temperature you need to cool the air to in order for it to be completely saturated with water vapor ( meaning 100% humidity). The air above us can hold only so much water vapor, and that amount is highly dependent upon the temperature (it’s also dependent upon other things, but let’s keep those the same and just talk about changing temperature).  

Put simply, warmer air can hold more water vapor than colder air. So, let’s take the air above us at a certain temperature, and with a certain amount of water vapor in it. If you start cooling the air but keep the water vapor the same, the air’s total capacity to hold water vapor starts dropping.  If you keep cooling it, at some point you’d get to a temperature where the air cannot hold any more water vapor than what it is currently holding.  At that point, the humidity is 100%. So, increasing dewpoint temperatures mean that water vapor is increasing…it’s getting more humid.  

In the summer, generally speaking, dewpoint in the 50s (10 to 15 degrees Celsius) are very comfortable.  As we rise through the 60s (16 to 20 degrees Celsius), it gets increasingly uncomfortable.  And dewpoints in the 70s are downright oppressive.  By the way, since the temperature cannot EVER fall below the dewpoint temperature, higher dewpoints mean warmer overnight lows since the air cannot cool as much as with dry air overhead.

Now, take a look at the dewpoint forecasts for each of the next five afternoons:

As you can see, our humidity misery will increase substantially by this weekend into early next week.  Get set to sweat.  Here’s the rest of the forecast…

Mostly sunny on Friday, with highs in the mid 80s (29 degrees Celsius).  As you saw on the dewpoint map above, we’ll still have very comfortable dewpoints on Friday.

Becoming partly cloudy Friday night, with those dewpoints starting to come up, as lows only drop into the upper 60s (20 degrees Celsius).  

Partly cloudy on Saturday with a scattered thunderstorm possible…better chances are over the northern half of the area. Highs near 90 degrees (32 degrees Celsius).  

Warm and muggy Saturday night, with lows in the low 70s (22 degrees Celsius).  

Mostly sunny, hot and very humid on Sunday and Monday, with highs in the mid 90s (34 degrees Celsius). The humidity could easily make it feel like over 100 degrees (38 degrees Celsius) in the afternoon.

A cold front will slowly slide down either Tuesday or Wednesday, bringing thunderstorms but, more importantly, cooler and drier air by the middle to end of next week.

Copyright 2018 by WDIV ClickOnDetroit - All rights reserved.