How Can an Eclipse Impact the Weather?

The August 21st solar eclipse is coming up soon, and although central Illinois will not be in the area of totality, about 90-95% of the sun's disk will be covered around here. This is still enough that weather conditions will be impacted.

How does an eclipse impact the weather? To see an example of this, we look back to May 10, 1994, when an annular eclipse crossed central Illinois. In an annular eclipse, the size of the moon is not big enough to cover the entire sun, so a ring of light appears around the sun's fringes. The maximum eclipse was observed at 11:56 am in Springfield, around the time of the routine hourly observation at Capital Airport. The hourly temperature observations showed a steady rise much of the morning, but temperatures fell 4 degrees between 11 am and noon despite a nearly clear sky.

The automated weather stations in use today at airports can be interrogated to get minute by minute values, so we can better observe the temperature trend with the upcoming eclipse.