The IEM produces a NWS COOP valued added dataset that contains estimated values when a NWS COOP site values to report one day. There's also a lot more to it than just that, but the purpose is to provide a complete time series without missing values.

In some instances, these virtual sites tracked NWS COOP sites that only reported temperature or precipitation, but not both. I've made a change now to no longer track these sites as "real-time", meaning these sites are no longer available with up-to-today data. This change removed 1,268 such sites. There are still 5,466 real-time sites available via the IEM, so take heart!

As a general comment, significant improvements were made to this workflow/dataset over the course of 2021 with smaller variances now against similar datasets provided by ACIS. Feedback and variance reports on this dataset are always welcome!