Here is a great graph produced by SCRD staff showing the timeline of bringing in water restrictions over the last six years. Blue is Stage 1, yellow is Stage 2, orange is Stage 3 and red is Stage 4.
As you can see, there is a big variation from year to year in terms of weather conditions and water supply. In 2017 our fall rains did not start until nearly November, and we went to Stage 4 in October. (Click on the image below to open a larger version.)