The Fargo-Moorhead area averages one thunderstorm day in October. This is somewhat misleading because it is just an average.
Some years, there may be three or four days or nights with thunderstorms. Then, several Octobers might pass with no thunder being reported at all.
Although the progression of the seasons is generally about the same every year, the actual daily weather varies quite a bit. Summerlike warm and humid conditions are certainly not as common in October as they are in July, but it is not unusual for there to be enough ingredients for thundershowers.
Severe weather in October is much more unlikely. However, severe weather is possible anytime the correct ingredients in the atmosphere come together, no matter what the season.
Thunderstorms with damaging wind, large hail and even a tornado are possible, if extremely rare, as we progress through the month of October.