Every summer we get a handful of emails asking about heat lightning. There’s really no such thing as “heat lightning” but rather it’s lightning that’s visible at night from a distant thunderstorm. Occasionally these storms can be seen more than 100 miles away! Here’s the AMS Glossary definition.
Nontechnically, the luminosity observed from ordinary lightning too far away for its thunder to be heard.
Since such observations have often been made with clear skies overhead, and since hot summer evenings particularly favor this type of observation, there has arisen a popular misconception that the presence of diffuse flashes in the apparent absence of thunderclouds implies that lightning is somehow occurring in the atmosphere merely as a result of excessive heat.
Last night, between 9 p.m. and 10 p.m., lightning was observed in Windsor Locks at Bradley International. Props to the contract weather observer for augmenting the ob!
KBDL 050151Z COR 20008KT 10SM FEW030 27/22 A3015 RMK AO2 OCNL LTGICCC DSNT NW-N CB DSNT NW-N MOV E SLP210 T02720222
KBDL 050051Z 19012KT 10SM FEW040 SCT200 SCT250 28/23 A3013 RMK AO2 SLP202 CB DSNT NW QSTNRY T02830228
That “heat lightning” was from a thunderstorm west of Canajoharie, NY in the Mohawk Valley of upstate New York along the New York State Thruway – 140 miles northwest of Bradley!
The thunderstorm wasn’t even particularly impressive when lightning was observed in Connecticut. A weather watcher in Tolland also reported distant lightning. An observer of “heat lightning” won’t hear thunder as the thunder will dissipate long before traveling that distance.
If the storms tonight over southern Vermont hold together we may see some distant lightning to the north and northeast. Keep an eye out!