1. Lighting can strike twice. The empire state building in New York has been struck by lightning as many as 48 times in one day.
2. The average flash of lightning would light a 100 watt light bulb for three months.
3. Lightning can strike in volcanic ash clouds. Not much is known about volcanic lightning, but we’re using it to help track ash clouds.
Volcanic lightning
4. Thunderstorms can trigger asthma. The Met Office has worked with the NHS and Asthma UK to try and understand why.
5. The most thundery part of the earth is the island of Java where the annual frequency of thunderstorms is about 220 days per year.
Official blog of the Met Office news team 
What’s a 100 watt light bulb, grandad?
The watt is a derived unit of power in the International System of Units, named after the Scottish engineer James Watt. The unit, defined as one joule per second, measures the rate of energy conversion or transfer.
In this case it would be 100 per second.