Hot and humid conditions, along with the arrival of a weather front, created the right conditions for thunderstorms in the Maritimes on the weekend. The heat and moisture are the “fuel” for the thunderstorms, and the weather front is the “trigger.” The front acts to start the initial “lift off” of the air near the surface that then rises rapidly and starts the strong atmospheric convection that develops the storm clouds, known as cumulonimbus. Some of the thunderstorms on the weekend packed very frequent lightning and downpours, at times accompanied by severe thunderstorm watches and warnings. I also had a few incidents of “heat lightning” reported to me. So, what is “heat lightning” and is it any different than regular lightning? The quick answer is that it is not different at all. Instead, it is a result of spotting some of the lightning flash of a very distant, over the horizon thunderstorm. The distance from the storm prevents seeing the lightning striking out from it. The flashes seen are usually due to intracloud lightning in the very highest part of the storm that is still visible over the horizon or by the lightning flash being reflected by even higher clouds in the atmosphere. Due to the distance, thunder is not audible. The sound waves created by the lightning strike dissipate before reaching the observer. These conditions are most frequent in the summer and on some of the hotter days when there is ample energy to fuel strong, longer-lived thunderstorms. The combination of no apparent storm cloud, no audible thunder, and heat lead people to the term “heat lightning.”
