How does the number of climate stations, or rain gauges, that are in operation affect the number of observed extreme events. Well, let's look at Toronto for example. Several past extreme events were reported in the Staff Report on Impact of July 8, 2013 storm on the City's Sewer and Stormwater Systems dated September 6, 2016: (https://www.toronto.ca/legdocs/mmis/2013/pw/bgrd/backgroundfile-61363.pdf)
During the May 12, 2000 extreme rainfall event, Toronto operated 16 rain gauges as shown on the staff report map below.
Fifteen years later, during the August 19, 2005 storm, the City operated 31 rain gauges as shown below, so almost double the number of rain gauges. Look at the higher density of gauges in north Toronto where many higher August 19, 2005 rainfall depths were observed.