Complex sentence: Being in May, low pressure systems produced large contrasts of temperatures which add more ingredients for the development of powerful thunderstorms with possible damaging tornadoes such as it was the case on May 10,1905.
Split into simpler sentences: Being in May, storm systems produced large contrasts of temperatures, which added more ingredients for the development of powerful thunderstorms with possible damaging tornadoes. Such was the case on May 10,1905.