I learned so much about tornado science and storm chasing while researching this book. Here are the answers to just a few questions that might be on your mind.

Where do tornadoes strike?

Tornadoes have touched down in every part of the world except Antarctica (as far as scientists know). But the vast majority of tornadoes happen in the United States. Since scientists started keeping track, the United States has been struck by ten times as many tornadoes as Canada, which ranks second. Half of all US tornadoes hit in the central plains; the area from northern Texas to North Dakota has often been called Tornado Alley. The South is another tornado-prone area in the United States. Mississippi has actually been hit by twice as many tornadoes as Kansas. But every state except Alaska has been struck by tornadoes.

How often do tornadoes strike in the United States?

An average of 1,000 tornadoes touch down in the United States every year. But in some years, there are far more. The year 2011 was unusually active; 1,691 tornadoes touched down, including 758 in April alone. On April 27, 2011, 200 tornadoes struck in that one day, the largest daily total ever recorded.

What causes tornadoes to form?

Scientists have been studying tornadoes for 150 years, but these storms remain one of the great mysteries of science. We know that tornadoes are created within violent supercell thunderstorms. But not all supercells give birth to tornadoes, and scientists have no way of predicting which storms will unleash deadly twisters and which ones will fade away.

What do storm chasers really do?

Storm chasing is very dangerous, and nobody should attempt to chase a storm unless they are very experienced. Many storm chasers are scientists determined to learn more about how tornadoes work. Storm chasers are actually an important part of America’s tornado warning system. Weather forecasters don’t know for sure that a tornado exists until it actually touches down. Very often, the first to see a tornado are storm chasers, who notify police and weather forecasters so that people can be warned.

The character of Dr. Gage is based on three chasers I discovered in my research. Tim Samaras spent years trying to record sounds from inside tornadoes. And Jeff and Kathryn Piotrowski spotted the tornado as it was closing in on Joplin. It was Jeff who alerted the police, who called for the tornado sirens to be sounded for the second time that day. Very likely their work saved lives.

Tragically, Tim Samaras, who was famous for his caution, was killed in May 2013, when his car was overtaken by a rain-wrapped tornado in El Reno, Oklahoma.