English to Persian (Farsi) Science Meteorology Popular Expression about the Weather

Greetings,

Please, what do you call the sound of thunder? At the house of my Shirazi friend on Sunday evening we heard the sound of thunder outside the house and knew that shortly it would be pouring with rain.

The word used by my friend was قوتراق (qorterāq), but I find it nowhere. Perhaps it's dialect.

Best wishes, and many thanks,

Simon