1865 (pre): Shower of Rats in a Norwegian Valley
In Norway, a migration of rats was 'transported by the wind' and fell in an adjacent valley.
This simple account is from Charles Tomlinson's book, The Rain-Cloud and The Snow-Storm, published in 1865. Unfortunately, due to the lack of any other detail, it's basically impossible to track it down further (barring pure luck). I will add this bit of information though: Tomlinson's book is an expansion of one he wrote in 1846, just called The Rain-Cloud. So it's between 1846 and 1865 that Tomlinson himself first heard of this incident. He also says "it is recorded in the history of Norway;" so the incident may have been garnered from an obscure historic text in Norweigian. Oy.