Rolling Loess Prairies

Poweshiek County received 9.8 in of rain in September 2026, 5.9 in above the 1901-2000 normal of 3.9 in, ranking 5th wettest September of 132 on record. This exceptional rainfall follows the early-September dry spell and represents major moisture surplus this fall.

Poweshiek County recorded 2.6 in of precipitation through October 22, 0.9 in above the normal 1.74 in by this date. October is tracking toward above-normal rainfall for the month.

Grinnell 3 SW weather station 3 km away recorded a mean daily high of 71°F, 4.3°F above normal, and mean daily low of 48.9°F, 8.5°F above normal over the past 30 days. Above-normal temperatures persist well into late October, extending the warm autumn pattern.

A silphium borer moth (Papaipema silphii) was recorded on 2026-10-03 in Grinnell during its adult flight period. This threatened prairie specialist depends on Silphium plant roots for larval development and occurs in fragmented mesic prairie habitat. The observation indicates functional prairie habitat remains in the area where this rare Midwestern moth can persist.

No part of Poweshiek County is in drought as of the week of September 15–21, 2026. The absence of drought in this prairie county in late September reflects adequate moisture supplies through the summer months and the wet conditions reported at local weather stations, maintaining soil water reserves as the growing season closes.

Through September 21, Grinnell 3 SW received 4.9 inches of rain, 2.6 inches above the normal of 2.27 inches by this date. This surplus moisture follows dry conditions earlier in September, when the month ranked 23rd driest of 131 years on record.

The Grinnell 3 SW weather station 3 km away recorded a mean daily high of 82°F and mean daily low of 61.4°F over the past 30 days, running 3.9°F and 7.9°F above normal respectively. This persistent warmth represents one of the warmest periods of the year at a typical time when cool nights should dominate the transition to autumn.

Blanchard's Cricket Frog, a threatened amphibian, was recorded on 2026-08-24 at Kellogg in wetland habitat. This small frog's presence signals functional breeding habitat with dependable water supply, as they require reliable ponds and wetlands for their annual breeding cycle.

American Bumble Bee, a federally threatened species, was observed on 2026-09-06 in Gilman and on 2026-08-27 in Grinnell. This bumble bee is declining across much of its North American range, and its presence here during late summer indicates continued use of prairie and grassland habitat for foraging on native wildflowers.

Large Yellow Underwing, an introduced European moth, was recorded on 2026-09-20 in Grinnell. This species is highly migratory with large numbers sometimes appearing suddenly in marginal parts of its expanding North American range during fall.