Hurricane season is the time of year when hurricanes and tropical storms form in the Atlantic Ocean and Gulf of Mexico. Hurricane season lasts from June through November, with the most activity taking place from August through September. If a hurricane is strong enough, affected areas could be asked to evacuate.
Differences between a warning and a watch
A watch means that the potential exists for the development of severe weather. While no immediate action for the public is required for a watch, you should keep up to date on the current weather situation and be prepared to seek shelter if necessary.
A warning requires immediate action and should be taken seriously. It means that severe weather is imminent in your area or is already occurring, based on either human observation or detected by Doppler radar.
Listen closely to instructions from local officials on TV, radio, cell phones or other computers for instructions from local officials. Evacuate if told to do so.
- Hurricane watch: Be prepared
Alerts people that hurricane conditions with sustained winds of 74 mph or greater are possible. Because it may not be safe to prepare for a hurricane once winds reach tropical storm force, hurricane watches are issued 48 hours before tropical storm-force winds are expected.
- Tropical storm watch: Be prepared
Alerts people that tropical storm conditions with sustained winds of 39 to 73 mph are possible within 48 hours.
Listen closely to instructions from local officials on TV, radio, cell phones, for instructions from local officials. Evacuate immediately if told to do so.
- Hurricane warning: Take action
Issued to alert people when hurricane conditions with sustained winds of 74 mph or greater are expected. Issued 36 hours before tropical storm-force winds are expected. Warnings are issued to give you time to complete your preparations.
- Tropical storm warning: Take action
Issued to alert people that tropical storm conditions with sustained winds of 39 to 73 mph are expected within your area within 36 hours.
- Extreme Wind warning: Take action now
Issued to alert people when extreme sustained winds of a major hurricane, 115 mph or greater, are expected to begin within an hour. Take immediate shelter in the interior section of a well-built structure.
The formation of a hurricane
The formation of a hurricane happens in three stages:
- Tropical depression – when maximum sustained surface winds are up to 38 mph (33 knots).
- Tropical storm – an organized system of strong thunderstorms with a defined circulation and maximum sustained winds of 39-73 mph (34-63 knots).
- Hurricane – when sustained winds in a tropical cyclone equal or exceed sustained 74 mph (64 knots) or greater.
Hurricane related terms
- Eye – center of a hurricane with light winds and partly cloudy to clear skies. The eye is usually around 20 miles in diameter, but can range between five and 60 miles.
- Eye wall – location within a hurricane with the most damaging winds and intense rainfall.
- Storm surge – abnormal rise of water caused by a storm, over and above the predicted astronomical tide. It’s the change in the water level due to the storm. Storm surge is caused primarily by the strong winds in a hurricane or tropical storm. All locations along the U.S. East and Gulf coasts are vulnerable to storm surge because the surge can make its way well inland from the coastline.
- Category I – 74-95 mph winds with 4-5 ft. storm surge and minimal damage
- Category II – 96-110 mph winds with 6-8 ft. storm surge and moderate damage
- Category III – 111-130 mph winds with 9-12 ft. storm surge and major damage
- Category IV – 131-155 mph winds with 13-18 ft. storm surge and severe damage
- Category V – 155+ mph winds with 18+ ft. storm surge and catastrophic damage
How to prepare for a hurricane or tropical storm
- Have a family emergency plan.
- Know your evacuation route and where you’ll go if told to evacuate.
- Fill-up your car’s gas tank in case you have to evacuate.
- Make a go bag of emergency supplies in case you have to leave in a hurry.
- Protect your windows from high winds by covering them with pre-cut plywood or hurricane shutters.
- Bring in all outdoor furniture, decorations, garbage cans, and any other outdoor item that is not secured.
- Keep all trees and shrubs trimmed.
Sign up for ReadyPhiladelphia, the region’s emergency text and email alert system. The alerts are free but standard text messaging rates may apply.
Hurricane mobile app
The American Red Cross Hurricane App can help you prepare for a hurricane. The app allows you track to storms, prepare your family and home, find help, and let others know you are safe. The app is available to download on Android or Apple devices.
Hurricanes, tropical storms, nor’easters, and other coastal storms can also cause flooding and utility interruptions. Visit the City’s flood page to learn about flood safety tips.