October Climatology in the Tennessee Valley

Before we move forward, let’s take a look back at some rainfall stats across the area for the past month. Overall, September was a rather dry month across the Tennessee Valley. That is to be expected. It is one of the driest months of the year here, typically speaking. However, it was a good bit drier than our long-term averages. The climate reporting station at the Northwest Alabama Regional Airport in Muscle Shoals only saw 0.06″ of rain for the entire month. This is almost 3.5″ below normal, and this helps lock in a deficit for the year so far of almost -6″. Most of the area didn’t do much better. The majority of our viewing area saw near or less than an inch of rain for the month, with very localized exceptions being near Hohenwald, TN and Hartselle, AL. Still, even there, those locations averaged a good bit below normal, and many communities in our area half to only as much as one tenth of the rain they usually see for the month of September! That has eroded away a little bit at the moisture we got from all the persistent rain during the first half of the summer, and now the latest drought monitor outlook from the NWS Climate Prediction Center has much of our area in “abnormally dry” conditions. They have also outlooked our area for a “rapid onset drought” to develop as we head through the first half of October. October averages as our driest month of the year in the Tennessee Valley; so, there may not be a lot of relief in the rain department the next few weeks. The good news is that the weather usually does start getting much wetter and more active as we head into November and the jet stream heads southward again as we get into the cooler months of the year.

So, now we look ahead to October and what kinds of weather the new month may bring to the Tennessee Valley. To do that, a good starting point is to look at local climatology records for the region. This gives us a good baseline long-term “average” for the local area. The first thing we notice is that the month of October is when summer temperatures rapidly start fading away and we head toward the cooler shots of air coming from Canada. The average daytime high for the month overall is 74 degrees, with an average morning low of 50. However, those highs usually still average near 80 at the start of the month before making it down to the upper 60s by Halloween. October is usually when we start the classic parade of fall cold fronts from the northwest, but we don’t always cool quickly. As recently as 2019, we saw triple digits during the month, with a record high of 100 degrees for Muscle Shoals set in October that year! On the flip side, we can sometimes get pretty chilly this time of year if those Canadian cold fronts are aggressive enough. The record low for the climate station at Muscle Shoals is 23 degrees set back in 1917, and our average first frost across the area usually happens near or a few days before the end of the month.

As mentioned previously, October averages as the driest month of the year in the Tennessee Valley. We normally see just a bit shy of 3.5″ of rain for the month, although we can sometimes see much more than that with occasional heavy rain and storm events along cold fronts and with the occasional landfalling tropical system on the northern Gulf Coast. It’s too early in the cool season to have an average of any measurable snow across the area, but we have occasionally seen flurries or even a trace light dusting in spots as early as late in October some years!

As we briefly hinted at above, the tropics aren’t always shut down as we head into October. While we are past the peak of the Atlantic hurricane season, it doesn’t end until November 30th, and there is a second small climatological peak that happens during October. This is often from low pressure systems that form in the Caribbean or Bay of Campeche/southern Gulf of Mexico and then head north and northeastward ahead of advancing cold fronts and upper-level troughs of low pressure as the mid-latitude jet stream begins to get active again. While it doesn’t happen often, that means that there can sometimes be landfalling tropical storms and even hurricanes on the northern Gulf Coast in October. We only need to look to Hurricane Michael in 2018 and Hurricane Opal in 1995 to know how intense those can sometimes be, even if it is a rare occurrence overall.

As the jet stream begins to get more active and send cold fronts southward into our region, that means we start heading back toward our tornado season that begins in fall and lasts through the winter before peaking in frequency/intensity in spring. While the long-term numbers don’t make a significant upward jump until November, that activity does start to get going in October some years (and even occasionally late September without any tropical systems involved). And yes, of the few tornadoes that we have seen in the month of October over the years, some of them have been strong. The month of October has seen three (E)F3 intensity tornadoes affect our immediate viewing area (including one right through Florence, AL in the 1960s), as well as an additional EF2 strong tornado. This is just another reminder that we must remain severe weather ready at all times of the year, but especially during the core of our area’s tornado season that runs from the fall through spring.

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