31 million people live in the path of totality of the eclipse. Severe storms threaten visibility for 16 million in Texas, Oklahoma, Arkansas and Louisiana.
Scientists are preparing experiments "completely different from how we usually do them," according to NASA. The cities and towns where the total eclipse will be seen are packed with the arrival of tourists. The eclipse will take place between 2pm and 4pm ET on August 21 in the United States and 2pm GMT on August 22 in Mexico. The total eclipse is expected to last about two minutes and 40 seconds.