The Wisconsin Water Library at UW Madison has STEM and Literacy Together Kits to use for story time. The kits include traditional storytime elements (reading, songs, art activity), along with a water-related STEM aspect.
Available for request:
Once Upon a Pond (all about ponds in Wisconsin) – Call no. 071246
Jump Around with Frogs (Wisconsin Native Frogs and Toad) – Call no. 281686)
Does it Sink or Float? (Buoyancy) – Call no. 232434
They are available to request here, though some sleuthing indicates they are not on the regular catalog.