July has arrived! Here's a look at climatology for the month in the Tennessee Valley.
Rainfall across the Tennessee Valley for the last few weeks has been lacking. We've had a couple of days with widespread storms, but even those days haven't featured rain with everyone. For climatological stats in our viewing area, those are recorded at the Northwest Alabama Regional Airport in Muscle Shoals. Rainfall for June was over 4 inches behind, with less than an inch officially recorded at the reporting site for the whole month.
Many locations across the Tennessee Valley are only running with 50 to 75% of their normal rainfall for the past 30 days. Some locations have had as little as 20 to 45% of their average rainfall for the last month. A few locations, especially south of the Tennessee River, have gotten a little more in the way of storm activity the past couple of weeks and have rebounded closer to normal. These dry conditions, combined with the increased evapotranspiration during the couple of hot weeks we had in June, have led to drought conditions developing across the Tennessee Valley. This is mainly a shorter-term drought based on vegetation and rainfall totals, with the deep soil moisture not yet severely affected because we are near normal in rainfall for the year. However, we need to start turning this around over the next few weeks, or the drought will worsen.
Now that we are heading into July, we look ahead to what the weather may bring to the Tennessee Valley. We all know that July is most often a hot month here. Our average highs usually come in around the lower 90s, with our average morning lows near 70 degrees. We can certainly roast here at times though. Our all-time monthly record high is 108 degrees from back in 1930. On the other hand, cold fronts aren't completely unheard of either. It seems so hard to imagine, but the record monthly low was a chilly 49 degrees back in 1937!
We usually average around 4.3 inches of rain for the month, but this comes rather uneven because of the scattered hit-and-miss nature of showers and thunderstorms during the summer. It usually takes either a somewhat infrequent thunderstorm complex in northwest flow aloft or influences from a tropical system in order for us to get a widespread soaking where everyone gets heavy rain during a particular day this time of year.
As was the case with June, the vast majority of our severe thunderstorm activity in July either comes from the occasional thunderstorm complex with widespread damaging straight-line winds or from an isolated pop-up storm in the afternoon that may produce short-lived damaging winds or hail. If we see tornado activity in July, and it isn't often at all, it is usually associated with the remnants of a tropical system affecting our area. However, a stray occasional tornado within one of those storm complexes or from storms interacting with outflow boundaries from other storms isn't completely impossible. Since 1950, north Alabama has only officially recorded 19 tornadoes in the month of July, and since 1811, all of middle Tennessee has only officially recorded 23 tornadoes. Most of them are the short-lived, lower-end variety when they do occasionally happen. However, it isn't impossible to get an occasional strong tornado in the outer rain bands of a tropical system after it makes landfall.
Tropical activity in July is usually starting the upward trend, but we are definitely still located in the relative lower-activity part of the season prior to the peak. If we are going to see a system develop in July, it either happens off the East Coast or in the Gulf or Caribbean. This means that these systems can be threats to the United States. It's not unheard of to get a July system to develop from a wave off the coast of Africa, but that activity usually starts ramping up more in August, September, and October. Systems have a higher chance of making hurricane status in July as compared to June.