Bring a sweatshirt with you on August 21! During the eclipse, the temperature may change 1/2 or 3/4 as much as it regularly does at night, based on your location and climate. This will likely be 10-15 degrees, but it could be more.
When the Moon blocks sunlight from reaching Earth, Earth’s temperature drops. Since we want to understand this phenomenon better, NASA has invited eclipse observers around the country to take part in an experiment. In order to become a citizen scientist and participate, all you need is the free GLOBE Observer app and a thermometer.
You don’t have to be in the path of totality. You don’t even need good weather. As long as you are in North America, NASA can use the cloud and air temperature data you collect. If you are committed to observing the eclipse from beginning to end, this is a productive task you can perform during the stages of partial eclipse, and I would encourage you to do so.