The best source of information about the Spanish Flu I have found – short of a book – is the Wikipedia Spanish Flu page.
The Spanish Flu had three pandemic waves, which is shown on this chart of the weekly combined influenza and pneumonia mortality in the United Kingdom, 1918–1919. You can see there was an initial outbreak late spring 1918. Then a more deadly spike in the fall of 1918 which was stopped by social distancing. Then social distancing was relaxed and there was a third spike in early 2019.
It’s a long article but filled with useful information. It can be found at https://en.wikipedia.org/wiki/Spanish_flu