When severe weather events like flooding or hurricanes occur, you may hear terms like “100-year storm” on the news. The “100-year storm” label makes it sound like that amount of rain only falls once every 100 years, but 100-year storms can actually happen two years in a row or even multiple times in the same year.
A “100-year storm” refers to the amount of rainfall that has a 1 in 100 (or 1%) chance of occurring at that location in any given year. As of now in Pittsburgh, 2.56 inches of rainfall within 1 hour or 4.92 inches of rainfall within 24 hours would both be considered 100-year storms.
Storm sizes are estimated for each region based on a statistical analysis of local rainfall data. The Pittsburgh region only has 60 years of historical rainfall data, which makes the estimation of a 100-year storm less accurate. As we gather more years of rainfall data and as climate change continues to shift our weather patterns, the amount of rain associated with a 100-year storm in Pittsburgh will likely change.
During the Independence Day holiday, Dispatchers and Operations will be available to respond to water or sewer emergencies Thursday, July 4. If you experience an emergency, please call our 24/7 Emergency Dispatch at 412-255-2423 (Press 1).