How much rain can a hurricane make, and does the storm size matter?
Storms big and small can produce a lot of rain. What matters most is how fast they’re moving, as an atmospheric scientist and educator explains.
Hurricanes can generate staggering amounts of rainfall, with some storms dumping trillions of gallons of water. However, the primary concern is not the total amount of rain, but rather how much precipitation falls over a specific area. For instance, during Hurricane Harvey in 2017, a town in Texas received over 60 inches (152 centimeters) of rain over five days, causing rivers of water to fill empty swimming pools to a depth of 5 feet (1.5 meters).
Another example is Hurricane Lane in 2018, which dropped 58 inches (147 centimeters) of rain on Kahuna Falls, Hawaii.
Atmospheric scientist and educator from Georgia Tech explains that a hurricane's formation requires specific conditions, including a tropical thunderstorm complex, high moisture in the atmosphere, winds with minimal change in speed and direction with altitude, and warm sea surface temperatures. Specifically, sea surface temperatures of at least 80 degrees Fahrenheit (26.5 degrees Celsius) are necessary to fuel hurricanes, as the warmth allows for the evaporation of water into the air, providing energy and moisture to the storm.
The size of a hurricane can vary greatly, from small storms like Tropical Storm Marco with a radius of 11.5 miles (18.5 kilometers) to extremely large ones like Super Typhoon Tip in 1979, which spanned 690 miles (1,110 kilometers) in radius, or about 1,380 miles (2,222 kilometers) in diameter. Scientists are still investigating what factors influence hurricane size and rainfall, but they have found that hurricane size may be affected by the temperature of the ocean water compared to its usual level at that time of year.
Warmer-than-usual water can cause hurricanes to grow both in size and strength, as seen with Hurricane Helene in 2024. This powerful storm, near Florida, benefited from unusually warm water near the late September sea surface, allowing it to carry vast amounts of moisture inland, resulting in catastrophic flooding in North Carolina.
Written by urgent.news from The Conversation's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
