Last night I told you about the "first-order" weather observing network in this country, which consists of about 1000 mainly-automated sites that take observations of the weather each hour.

There's another national system of weather observers called the "cooperative observing network." This network is staffed by volunteers at more than 10,000 locations. Unlike the first-order network where weather observations are automated and taken once per hour, data at cooperative observing sites is collected by human observers, but only once per day - typically, an observer might take readings just after sunrise, noting the high and low temperature during the last twenty-four hours and any rain or snow that's fallen.

Because of this once-per-day observing schedule, data from the cooperative network isn't really used for forecasting, but rather mainly for climatological purposes. The Franklin Institute is a cooperative observing site, and there are plenty of other nearby sites in cities such as Newark and Lewes in Delaware, Valley Forge and Washington Crossing in Pennsylvania, and Moorestown and Glassboro in New Jersey.