как перевести "spell of" ? например spells of lightning?

Попроще: промежуток времени, когда что-то происходит. Разряды молнии.

A spell of a particular type of weather or a particular activity is a short period of time during which this type of weather or activity occurs.
There has been a long spell of dry weather...
You join a barrister for two six-month spells of practical experience.
...sunny spells.
Syn: period