After A Dry & Warm September, Temperatures Tumble

It has been a wonderful few weeks as temperatures finally fell out of the record high territory with September finally getting days with temperatures below average, even though it was only a day here or there.  Now that we are in October, its that time when temperatures fall even faster as average highs go from around 70 on the 1st to the low 50’s by Halloween.  This will spark very large temperature swings, as this month is arguably the worst when it comes to wild contrasts in temperature not only from day to day, but also from city to city.  It’s not uncommon to find high temperatures some 40 degrees different between our northwest to our southeast.  Just like October fashion, there will be one such swing going through our area during the middle of the week.  A large trough will dig into the Midwest allowing temperatures to soar out ahead of it, but plummet behind it, leading the area to near record cold toward the weekend. 

Here is a look at our wild swings in temperature through the month of September…. And yes, October gets worse!

The yellow line you see that is steadily falling is where the average temperatures should be located.  The jagged line is where the actual temperatures ended up.  Notice that the overall high temperatures were below average and the overall low temperatures were below average, but we still found wild swings in the numbers from one day to the next.

Notice that highs peaked pretty early near 100 degrees then fell toward the end of the month with highs in the 60’s for a couple of days.  In October, things can get worse where highs can range from the 30’s to nearly 100 degrees.  But these wild temperature swings will likely be even more drastic this year.  Why you ask?  For the answer, we come back to our favorite friend called drought… we just can’t escape it.  In the middle of a drought, there is far less moisture in the ground AKA water.  Water has a much higher heat capacity then rock does AKA soil.  Heat capacity is the ability of an object to change temperature.  It takes A LOT more energy to change the temperature of water then rock.  Think about how long it takes to boil a pot of water.  It takes high heat for more then ten minutes to get the water hot enough for a very slow boil.  But if you stick a rock in a microwave, in 30 seconds the rock will be too hot to touch.  So with less water in the soil, it takes far less energy to heat and cool the surface of the earth, therefore it has a similar effect on the air around it.  Which is why we average warmer then average days and cooler then average nights over the past couple of months.

Not only was September all over the place in temperature, but it set records when it comes to rainfall.  Well, actually for lack of rainfall.  Aberdeen, Mobridge, and Pierre all set records for the driest September on record with many other locations in the north and west ending September ranked in the top 10.  Here are some of the stats.

So, I have been mentioning that October is often worse then September and it may live up to its name this week.  Here is a peek at projected 850mb temperatures using the computer forecasting models for Wednesday afternoon.

Notice the low that develops in central SD shown by the giant “L”, and how it drags up lots of warm air out ahead of it but temperatures plummet behind it.  This could lead to one of these large temperature contrasts I was talking about with highs in the southeast closing on 90 degrees, but areas in the northwest are stuck in the 50’s. Now take a look at what 850mb temperatures look like Thursday afternoon and then again Saturday afternoon.

The cold air swings in Thursday, which drastically cools the area, but it gets even colder by the weekend as numbers continue to drop right through the day Saturday.  Take a peek at our forecast high temperatures for the next few days.  Please remember that these will change a little as the days get closer, but this will give you a general idea of just how much colder it will be.

Even as a meteorologist, knowing that its coming for days, I’m still shocked at how quickly things can change.  Break out the winter clothes because it is going to be a chilly few days.  Stay warm!