Houston 4 day rain vs. Seattle 3 month rain
The rainfall in the Houston area from Hurricane Harvey is unprecedented in the United States. One rain gauge measurement just outside the city, if confirmed official, would become the new national rainfall record for a tropical event at 51.88 inches. That eclipses the old record of 48 inches set in Midland, Texas during Hurricane Amelia in 1978. Only a measurement in Hawaii in 1950 of 52 inches technically tops the list, but that was before Hawaii was granted statehood.
The official measurements from Houston's airports had storm totals around 32 inches. That is such an incredible amount of rain, it's difficult to put into perspective. Even those who had lived through hurricanes in Texas before wouldn't have experienced anything like Harvey, much less those who are long time Northwesterners where that kind of rainfall is nearly climatologically impossible.
But to make a feeble attempt, I tried comparing Houston's hourly rainfall during Harvey with Seattle's daily rainfall totals during the heart of our rainy season. Our 6 month period between October and March was our wettest on record with about 20" falling between October and December and after a brief cold break in January, picked up again with another 20+ inches...from February to April.
So here is 92 hours of Houston rain versus 92 days of Seattle daily autumn and winter rain. It compares Houston hourly total on the left with a corresponding Seattle daily total, then date on the right. The columns repeat on the right side for the second-half of the period to keep the table from getting too vertical. But there were several hours in Houston that were wetter than our wettest days. Or just look at Houston's hourly totals by themselves, especially from late on the 26th to late on the 27th. Houston had more rain on the 27th (16.07") than Seattle's wettest month on record (15.63" / November 2006).