Solar Data for Grand Rapids, Michigan

Solar data for Grand Rapids, Michigan has been maintained since 1903. We are one of the few, if only, cities in the nation that maintains daily sunshine statistics that get published in National Weather Service products such as the Daily Climate Report (CLI), Monthly Weather Summary (CLM), Seasonal Climate Report (CLS), and Annual Climate Report. Solar data on this webpage is available in the following formats and will be updated once per month via comma separated value(.csv) files, typically within the first week of each month:

• Monthly percent possible sunshine that was observed (going back to July 1903)
• Daily percent possible sunshine that was observed (going back to January 1905)
• Daily minutes of observed sunshine (going back to August 1948)

Since 1903, the U.S. Weather Bureau (modernly called the National Weather Service) has operated the sunshine sensor at the location of the official government office, which currently is located next to the Gerald R. Ford International Airport. The period of record from the early 1950s up until 2021 features data produced from a photoelectric sunshine switch and its associated sunshine indicator display. It is unknown what instrument was in use prior to the early 1950s.

Beginning in the spring of 2021, the National Weather Service partnered with an area Cooperative Weather Observer to install an experimental sunshine recorder at the government office. The sensor, much like the old one, has a sensitivity setting that will trigger a recording of sunshine if enough visible light impacts the sensor. Generally speaking, if any shadows are cast outside (even from faint, filtered sunshine), the device will count that as reportable sunlight and begin "ticking the minutes" until the sunlight drops below the sensor's threshold. After months of testing, this new sunshine recorder replaced the old photoelectric sunshine switch and is now the producer of daily sunshine data.

Data Access

Click the following links below to access monthly and daily historical solar data for Grand Rapids, Michigan. Note: These files will be updated once per month, typically within the first week of each month.

Grand Rapids Monthly Sunshine Data     Grand Rapids Daily Sunshine Data     Grand Rapids Daily Sunshine Minutes