It's been a thunderstorm-y year in New York City (2019), which suits me because I grew up in Omaha, NE where there are lots of bone-shaking thunderstorms. But I'm always curious to know when "thunderstorm season" is going to roll around, and this year I tried to dig for publicly available data on when lightning/thunder have happened in the past.
It turns out that the National Weather Service does collect this data, but it contracts with a private company to do it. The resulting legalistic gotcha aspect of this data is that the precise location of where individual lightning strikes happen is only made available to people with a ".gov" or ".mil" email address (rude!). But! The National Weather Service did manage to extract some kind of compromise, where aggregate totals of this data are made available publicly for free for 0.1 degree map tiles.
You can search below for a named location in the USA. This will show a map for that location illustrating the aggregate lightning area covered by the National Weather Service's data, as well as the daily count of lightning strikes within that area for the past five years. (the graph for the count draws from this d3 example)