How much rain can a hurricane make, and does the storm size matter?
Hurricane Harvey dropped several feet of rain on Texas, stranding trucks, people and their pets. Scott Olson/Getty Images Curious Kids is a series for children of all ages.
Hurricanes can produce enormous amounts of rain, sometimes trillions of gallons of water. For example, Hurricane Harvey in 2017 dropped over 60 inches (152 centimeters) of rain in Texas over five days, filling empty swimming pools 5 feet (1.5 meters) deep. Similarly, Hurricane Lane in 2018 dumped 58 inches (147 centimeters) of rain in Hawaii. The total rainfall from a hurricane depends on how long it lingers over an area rather than just its overall size. A slow-moving hurricane like Harvey can cause more localized flooding than a fast-moving one, even if both carry the same amount of moisture. The key factor is the duration of rainfall in a single location, not the storm's total volume of water.
Hurricanes form when several conditions are met: a tropical thunderstorm complex, high moisture in the air, consistent wind speeds with little change in direction or speed with height, and warm sea surface waters. The warm ocean water, at least 80 degrees Fahrenheit (26.5 degrees Celsius), is crucial because it evaporates into the air, providing energy and moisture to fuel the storm. For instance, warm water extending deep below the surface can significantly increase a hurricane's strength and size. The National Oceanic and Atmospheric Administration (NOAA) monitors these conditions to predict hurricane formation and intensity.
Hurricanes vary greatly in size. The average hurricane spans about 300 miles (482 kilometers) in diameter, but some can be much larger or smaller. For example, Super Typhoon Tip in 1979 had a radius of 690 miles (1,110 kilometers), making it half the size of the contiguous U.S. states. In contrast, Tropical Storm Marco in 2008 had a radius of just 11.5 miles (18.5 kilometers), comparable to New York City. Recent research in 2025 suggests that hurricanes tend to grow larger when they move over ocean water that is much warmer than usual for that time of year.
Both large and small hurricanes can cause significant damage, but their impacts differ. Large hurricanes like Hurricane Helene in 2024, which grew over unusually warm waters near Florida, can carry vast amounts of moisture far inland, leading to catastrophic flooding in areas like North Carolina. Small hurricanes, such as Hurricane Andrew in 1992, can still be extremely destructive despite their limited size. Andrew, a Category 5 hurricane, destroyed over 25,000 homes in Miami and the Everglades. Similarly, Tropical Storm Allison in 2001 caused over $4 billion in damage in Texas without ever becoming a hurricane.
The highest rainfall totals from hurricanes occur when storms move slowly or stall over an area, allowing rain to accumulate continuously. Hurricane Harvey in 2017 stalled over Texas for days, drawing moisture from the warm Gulf of Mexico and dropping up to 60.58 inches (1.54 meters) of rain in some areas. In contrast, fast-moving hurricanes like Hurricane Michael in 2018, which hit the Florida Panhandle as a Category 5 storm, produced rainfall totals of only 6 to 10 inches (15 to 25 centimeters) along its path. The speed of the storm is therefore a critical factor in determining local rainfall impacts.
Rapid intensification occurs when a tropical storm's maximum wind speed increases by 30 knots (about 34.5 miles per hour or 55 kilometers per hour) or more within 24 hours. This phenomenon can make hurricanes more dangerous and harder to predict. Hurricanes Harvey, Michael, and Helene all experienced rapid intensification before making landfall, catching coastal residents off guard. Accurate forecasting is essential to help communities prepare for these intensifying storms. Improving prediction models is an active area of research to enhance early warnings and reduce risks.
