The keepers of the oldest known official Illinois weather records relied on glass thermometers and observations, but recent research finds their data to be remarkably accurate.

State climatologist Jim Angel and an assistant recently researched the records. They were recorded in the 1820s and '30s with quill and ink at what was once known as Fort Armstrong on Rock Island.

Angel said the readings show temperatures not far from current averages. He said that means they were likely pretty accurate.

But the readings also come with observations like crop conditions and the sight of ducks flying south. On July 21, 1820, there was a "violent hurricane." Angel said that must have been high winds or maybe a tornado.