If it felt abnormally cold for the first week of May, you are absolutely right!
In fact, Friday was officially the coldest May 5th on record for the Huntsville Area, as daytime temperatures hovered in the low 50s (the official high hit the books as 53 degrees).
Friday’s high is not the ‘coldest’ May day on record for Huntsville — that date was May 3, 1921. On that day, the high was 49ºF (about 4 degrees cooler compared to May 5, 2017) and the low was 44ºF.
And to be sure, low-to-mid 50s for a high are not normal for the first week of May. Instead, these are the average highs for early February! In contrast, average highs for early May are in the upper 70s to low 80s.
To add further insult: Just seven days ago, daytime high temperatures were in the upper 80s! And last Saturday, thermometers at Huntsville International Airport reached 91 degrees!
So what was the culprit for the extreme cool down?
A surface low pressure system slowly moved over the Tennessee Valley, pulling cold Canadian air south into the region. Temperatures from the source region were also in the 40s and 50s, and combined with the overcast skies and cold rain over the Valley, an almost winter-like pattern set up over northern Alabama and southern Tennessee.
The good news is that the pattern is short-lived, but because the surface low is leaving overnight Friday/early Saturday, temperatures are expected to drop into the upper 30s/low 40s for Saturday morning.