June 1 is the official start of hurricane season in the Atlantic Ocean, lasting through November 30. As the storm season heats up, here are 15 things you should know: 

1. 2016 WILL PROBABLY SEE MORE STORMS THAN RECENT YEARS.

There have been fewer storms than normal in the last three years, according to the National Oceanic and Atmospheric Administration, so while forecasters say this year’s storm numbers will probably be around normal (with 10 to 16 named storms), that would still mean more hurricane activity than we’ve been used to recently. 

2. THE DIFFERENCE BETWEEN TROPICAL STORMS AND HURRICANES.

Hurricanes are very strong tropical storms. A tropical storm is defined as an organized thunderstorm system with winds between 39 and 73 miles per hour. Once winds hit 74 miles per hour, the storm is then characterized as a hurricane.

3. THEY ONLY FORM IN HOT WATER.

Tropical storms and hurricanes are powered by interactions between warm water and warm air. Because of that, they only form in the tropical region between 5 and 20 degrees latitude. Elsewhere, the ocean isn’t warm enough to form hurricane-strength storms. 

4. STORMS IN DIFFERENT HEMISPHERES ROTATE DIFFERENTLY.

Storms in the Northern Hemisphere rotate counter-clockwise, and storms in the Southern Hemisphere rotate clockwise. This is because of what’s called the Coriolis Effect, the result of the Earth’s rotation. 

5. HURRICANES CAN HANG OUT TOGETHER.

Called the Fujiwhara effect, when two storms get too close together (estimated at around 900 miles apart), they begin to rotate around each other like ice skating partners.

6. THE DIFFERENCE BETWEEN STORM ALERTS.

Hurricane or tropical storm watches mean that weather conditions make it likely that there’s going to be a hazard. These are issued 48 hours before authorities think storm-force winds will reach the area. A warning, on the other hand, means that the tropical storm or hurricane is expected to hit your area, and come 36 hours before the anticipated onset. Meanwhile, an extreme wind warning means that hurricane-force winds of more than 115 miles per hour are expected within the subsequent hour, so you should take shelter somewhere stable immediately. 

7. WHAT THE CATEGORIES MEAN.

The Saffir-Simpson Hurricane Wind Scale was created in the 1970s by a Florida engineer and the then-director of the National Hurricane Center, and rates hurricanes based on their wind speed. In 2012, the wind speeds for the categories were altered slightly to make it more accurate when converting from knots to miles per hour. A larger number means a more intense hurricane: a Category 1 hurricane will inflict some damage to houses while a Category 5 will destroy a significant number of houses. Any storm Category 3 or above (with winds 111 miles per hour or higher) is considered a major hurricane. 

8. WHETHER YOU’RE AT RISK FOR FLOODING.

To best prepare for storms, check to see whether you live in a flood or storm surge zone. The federal government has several websites designed to help you figure out your risk of flood hazards. You can just search your address and the database will tell you whether you’re at low, moderate, or high risk of flooding. 

9. WHAT YOUR PLAN IS.

You and your family should have an emergency plan that includes where you will meet if you get separated during an emergency, how you’ll get in touch if your phones don’t work, where you’ll go if you need to evacuate, and how you’ll get there. 

10. WHERE YOU CAN GO TO TAKE SHELTER.

Figure out where you should go in the event of an extreme wind warning. “Safe rooms” are extra-protected via design elements meant to withstand high winds and the debris that comes with them. In some places, there may be a community safe room near you, such as in a school. In others, it may be wisest to build your own safe room in your home using FEMA’s guidelines. Though basements seem hardy, you probably don’t want to shelter there during a hurricane, since it’ll be the first part of your house to flood.

11. WHAT TO KEEP ON HAND.

You should have three days’ worth of supplies on hand in case of an emergency. The U.S. Department of Homeland Security recommends keeping at least one gallon of water per day per person in your household. You’ll also want to collect a battery-powered radio, flashlight, first aid kit, moist towelettes, garbage bags, a can opener, maps, toiletries and medications, and other necessities in a safe place. 

12. WHO YOU’LL NEED TO CALL.

In the wake of a particularly bad hurricane, you may need to get in touch with emergency personnel, your electric company, your insurance agent, etc. Make sure you have numbers for hospitals, important utilities, your property insurer, and that out-of-town relative you’re hoping will relay news of your safety written down someplace safe, where you’ll be able to find them even if you have to evacuate.

13. WHAT YOU’LL DO WITH YOUR PETS.

Can you evacuate with Fido? Will he fit with you in the safe room? And if things get a little crazy, will you even be able to find Fluffy? Keep pet food in your emergency kit, and don’t forget a can opener if you need one. When the storm hits, even if you’re staying home, put your pet in a carrier in case you have to evacuate last-minute. And microchip your cat or dog so that in the event you get separated, vets and rescue personnel will be able to track you down. 

14. HURRICANES DON’T ALWAYS COME IN SEASON.

The first hurricane of 2016 arrived in early January, when Hurricane Alex formed in the Eastern Atlantic Ocean, the first Atlantic hurricane in that month since 1955. 

15. STORM PREDICTION IS NOT AS PRECISE AS YOU’D THINK.

It’s easy to assume that modern science has gotten to a point where scientists should be able to figure out what a storm will do long before it arrives. But there’s a lot about storm forecasting that’s still imprecise. Hurricane models rely on millions of different factors regarding conditions in the ocean and atmosphere. While forecasters are pretty good at modeling where a storm will travel based on large-scale conditions in the atmosphere, it’s hard to discern how intense it will be when it makes landfall, given how smaller-scale conditions like water temperature or wind direction change as the storm moves. That said, you should always be mindful of weather advisories. Even a slightly uncertain prediction from professional storm researchers is more accurate than your gut feeling.