Iowa Weather Check: Des Moines Temps Cool to 55°F on May 21
Temperature of about 55°F at KDSM at 18:10 UTC on May 21, 2026
Dewpoint of about 41°F at KDSM at 18:10 UTC on May 21, 2026
Barometric pressure of about 30.2 inches of mercury at KDSM at 18:10 UTC on May 21, 2026
What changed
The National Weather Service observation at KDSM logged a temperature of about 55°F at 18:10 UTC on May 21, 2026. The dewpoint came in at about 41°F at the same time, pointing to relatively dry air. Barometric pressure was about 30.2 inches of mercury.
This is a single-station snapshot — it reflects conditions at Des Moines International Airport, not a statewide average.
Why it matters
Late May is a key window for corn and soybean emergence across Iowa. Soil temperatures and air temperatures in the mid-50s°F range are worth watching because crop development can slow when temps stay below the upper 50s for extended stretches. A 55°F reading on its own is not unusual for a single afternoon observation, but if cooler-than-normal conditions persist, it could affect the pace of early-season crop growth.
The low dewpoint (about 41°F) suggests dry air was in place, which may matter for evaporation rates and surface moisture conditions.
What to watch next
- Multi-day temperature trends: One cool reading is routine; several days of below-normal temps could slow emergence. Check your local forecasts and soil temperature monitors.
- Upcoming precipitation: Dry air at the surface could signal a stretch without rain. Local soil moisture conditions are worth keeping an eye on.
- Statewide crop progress: USDA's weekly Crop Progress report (typically released Mondays) will show how Iowa corn and soybean emergence compares to the five-year average.
Source notes
- Temperature, dewpoint, and pressure data from the U.S. National Weather Service API — KDSM station latest observation (source).
Get the WASDE in your inbox — minutes after USDA drops it.
Every supply-and-demand table that moved, with the underlying USDA links. Free. Unsubscribe anytime.
More from this desk
- Weather · July 17, 2026Iowa 7-Day Forecast: Sustained Heat — Highs 92°F to 96°F Through July 22
Iowa is looking at a prolonged heat run: daytime highs of 92°F to 96°F from Thursday through Monday, with overnight lows mostly in the low-to-mid 70s. Tuesday eases to 87°F. That's five consecutive days above 90°F during peak corn pollination and early soybean pod-set timing.
- Weather · July 16, 2026Iowa 7-Day Forecast: Highs 92°F to 97°F Through July 20
Iowa's NWS forecast shows daytime highs ranging from 92°F today (July 13) up to 97°F on Friday, with no real break in sight through Sunday, July 20. Overnight lows hold in the 68–75°F range, which limits nighttime cooling for corn and soybeans during a critical stretch of the growing season.
- Weather · July 14, 2026Iowa 7-Day Forecast: Highs Climb From 89°F to 96°F Through July 18
Central Iowa daytime highs start at 89°F today (July 12) and ramp up to 95–96°F from Wednesday through Saturday, with overnight lows mostly in the low-to-mid 70s. That's a sustained heat stretch landing right in the corn pollination window.
- Weather · July 12, 2026Iowa 7-Day Forecast: Highs in the Mid-80s to 90°F Through July 11
Central Iowa daytime highs run 85–90°F through Friday, July 11, with overnight lows in the mid-to-upper 60s. Wednesday, July 8, is the warmest day in the forecast at 90°F.