National Weather Observers Day is celebrated every May 4 worldwide to honor individuals who enjoy observing the weather and contribute to the National Weather Service (NWS) in protecting lives and property. The day was founded in 1989 by Alan Bruce and is recognized by the NWS, although it has not been officially proclaimed nationwide. It acknowledges the historical significance of weather observation, which dates back to ancient civilizations and evolved significantly during the Renaissance with the introduction of measurement instruments. Modern weather agencies, including the NWS, rely on a network of volunteer observers, such as those in the Cooperative Observer Program (COOP) and Skywarn®, to report various weather conditions. Participants can also use the mobile app mPING to submit weather observations. Celebrating this day can involve learning more about weather observation and engaging in this hobby. Other related observances include Observe the Weather Day on January 25 and Skywarn® Recognition Day on the first Saturday in December.