Temperatures across Iowa were cooler than the previous reporting period, though still several degrees above normal. Portions of northern Iowa reported positive departures of up to six degrees; the statewide average temperature was 75.4 degrees, 3.1 degrees above normal. Moderate to heavy rain fell across eastern Iowa where several stations measured at least two inches of above average totals. Western Iowa remained unseasonably dry with departures approaching two inches below normal.
Southerly winds and cloudless skies boosted Sunday (19th) afternoon temperatures into the mid 90s in western Iowa while eastern Iowa experienced mid to upper 80s. Stars were shining overnight into Monday (20th) with morning temperatures well above average, ranging from the upper 70s northwest to low 60s southwest. Sweltering conditions developed into the afternoon hours as dewpoint temperatures pushed into the low to mid 70s, creating triple-digit heat index values in the presence of mid 90-degree air temperatures and clear skies; the statewide average high was 93 degrees, 11 degrees above normal. Anomalously warm morning temperatures remained into Tuesday (21st) with lows in the mid to upper 70s over most of Iowa under starry skies. A dry cold front pushed through Iowa during the daytime hours, shifting winds to a northwesterly direction and lowering the humidity. Temperatures remained in the upper 80s north to mid 90s south, though conditions were appreciably less muggy behind the front. Ample instability was present in southeastern Iowa to fire strong to severe thunderstorms along the surface boundary later in the evening. Several stations in south-central Iowa measured at least 0.50 inch of rainfall with Rathbun Dam (Appanoose County) reporting 1.36 inches. Skies cleared overnight into Wednesday (22nd) with winds becoming light and northwesterly. The incoming airmass was dry and pleasant, allowing afternoon highs to peak in the mid to upper 80s. Partly cloudy conditions developed in southwestern Iowa into Thursday (23rd) with overnight lows dropping into the low to mid 60s statewide. Showers skirted to the Iowa-Missouri border just after noon before dissipating in the late evening. Daytime highs varied from the upper 70s southwest to the low 90s north and west.
Thunderstorms formed in western Iowa later in the night and persisted across central Iowa into Friday (24th) morning. The complex lost some energy as showers moved into eastern Iowa into the afternoon hours. Several stations in Polk and Story counties measured from 1.07 inches to 1.50 inches. A secondary, narrow line popped up in southern Iowa during the evening hours. The main disturbance fired thunderstorms in the northwest and stretched over northern Iowa overnight into Saturday (25th) leading to flooding in Sioux and O'Brien counties. Heavy rainfall associated with stronger thunderstorms was also reported in eastern Iowa with 44 stations across the state observing at least an inch of rainfall; Iowa City (Johnson County) measured 3.75 inches while the statewide average total was 0.81 inch. An additional line of thunderstorms formed along and ahead of a cold front during the late afternoon hours dropping heavier rainfall in eastern Iowa with Muscatine (Muscatine County) picking up 1.36 inches. Overnight lows into Sunday (26th) cooled into the upper 50s in western Iowa while low to mid 60s were observed in eastern Iowa.
Weekly precipitation totals ranged from no accumulation at several western Iowa stations to 4.25 inches at Iowa City (Johnson County). The statewide weekly average precipitation was 0.91 inch while the normal is 1.05 inches. Multiple stations reported the week's high temperature of 99 degrees on the 20th, 21st and 22nd, on average 16 degrees above normal. Audubon (Audubon County) reported the week's low temperature of 50 degrees on the 26th, six degrees below normal.
Categories: Iowa, Weather