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Typically, peak hurricane season lasts from the end of August to mid-September, when water temperatures rise above 82 degrees (as indicated by the orange highlight). This NASA map of water temperatures tracked during Hurricane Katrina shows why that storm picked up intensity over the Gulf of Mexico and why Ophelia gained strength in the Atlantic Ocean.
Hurricane Ophelia as seen from a window in the International Space Station.
The Tropical Rainfall Measuring Mission (TRMM) shows the rainfall from Ophelia on Sept. 11, when it was rated as a tropical storm. The blue columns indicate areas that were hit by more than a quarter-inch of rain per hour, green indicates more than a half-inch per hour, yellow more than an inch per hour and red more than two inches per hour.