The current weather data collected for a given day consists of:

1. The maximum temperature (F°) over a 24 hour period.
2. The minimum temperature (F°) over a 24 hour period.
3. Amount (in inches) of rain, melted snow, etc. that fell in the previous 24 hour period. (This includes snow and ice reported in #4 -- melted to ascertain their liquid equivalent.)
4. Amount (in inches) of snow and ice pellets that fell in the previous 24 hour period.
5. The level (in inches) of the snow, ice pellets, hail, ice on the ground at the Observatory.

Historical data may contain different information.  At times the wind speed was recorded, as was the humidity.  When data collection was started, temperatures were recorded at specific times -- morning, noon, and evening -- rather than high and low for the day.  There have been many changes over the years.

Online data is currently available from 1950 to the current year, as well as for scattered years going back to 1827.  We are in the process of digitizing the historic data, and it will be added to this site as we progress.  All the data is also available for viewing in hard copy format at the Rauner Library.

For more information about the weather archive, please email Alan Goldblatt with any questions you have.

For years prior to 1950, data is available as pdf images of the originals, preserving the historical information.  For the years 1950 through the year previous to the current year, the data is stored in zip files.  Each zip file contains all of the weather data, stored as monthly xls or xlsx files, for a given decade.  Individual xlsx files are available for the current year.