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Weather & Climate in St. Marys, IA

Temperature, precipitation, air quality, natural hazards, and monthly weather data.

St. Marys experiences four distinct seasons with an average annual temperature of 50°F (10°C). Winters average 22°F in January while summers reach 75°F in July. The area gets 275 sunny days per year, well above the U.S. average of 205 / making it one of the sunnier locations in the country. Annual precipitation totals 37.8 inches. The area receives 30.8 inches of snow annually, a moderate snowfall amount. Air quality is rated Good with a median AQI of 43. The city sits at an elevation of 1,036 feet.

Temperature

22°F Jan (-6°C) 75°F Jul (24°C)
Annual Average49.9°F
8% below US avg
January Average22°F (-6°C)
July Average75°F (24°C)
Sunny Days275 days/yr

Geography

Elevation1,036 ft (316 m)
Area0.1 sq mi (0.4 km²)
Population Density800/sq mi
Coordinates41.3077°N, 93.7338°W
TimezoneAmerica/Chicago
CountyWarren County County
Nearest AirportDes Moines International (DSM)
13 miles away

Precipitation & Snow

Annual Rainfall 37.8"
1% below US avg
Snowfall 30.8"
Wettest Month (Jun) 4.57"
Driest Month (Jan) 0.91"

Air Quality

AQI Median43.0
RatingGood

Natural Hazard Risk

Overall RiskVery Low
Risk Score36.1 / 100
Social Vulnerability10.6 / 100
Community Resilience91.3 / 100

Hazard Breakdown

Tornado Relatively Moderate
Hurricane Very Low
Earthquake Very Low
Wildfire Very Low
Flood Relatively Low
Hail Relatively Low
Strong Wind Relatively Moderate
Heat Wave Relatively Low
Winter Weather Relatively Low
Lightning Relatively Moderate
Ice Storm Relatively Low
Drought Relatively High
Cold Wave Relatively Low
Landslide Relatively Low
Source: FEMA National Risk Index v1.20 (Dec 2025)

Earthquake History

1 earthquake (M2.5+) recorded within 150 km since 1990. Strongest on record: M3.1.

Feb 11, 1995 6 km E of Clearmont, Missouri M3.1 136 km 5 km
Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.

Tornado History

663 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF5. Total: 19 fatalities, 345 injuries.

Date Rating Distance Path Fatalities
Jun 13, 1976 EF5 70 km 21.3 mi 0
Jun 27, 1953 EF5 82 km 0.1 mi 1
Mar 5, 2022 EF4 40 km 70.6 mi 6
Apr 8, 1999 EF4 58 km 56.0 mi 0
May 27, 1995 EF4 93 km 30.0 mi 0
May 27, 1995 EF4 63 km 57.0 mi 0
May 24, 1989 EF4 90 km 49.0 mi 0
Sep 28, 1986 EF4 50 km 20.0 mi 0
Jun 2, 1980 EF4 78 km 31.2 mi 0
Jun 18, 1974 EF4 48 km 15.3 mi 2
May 20, 1959 EF4 84 km 17.2 mi 0
May 10, 1959 EF4 78 km 41.1 mi 0
May 10, 1953 EF4 59 km 6.4 mi 0
Mar 5, 2022 EF3 50 km 11.3 mi 1
Aug 20, 2019 EF3 18 km 5.4 mi 0
Jul 19, 2018 EF3 69 km 9.2 mi 0
Jun 22, 2015 EF3 54 km 11.1 mi 0
Apr 8, 1999 EF3 32 km 39.0 mi 0
May 27, 1995 EF3 85 km 30.4 mi 0
Apr 14, 1994 EF3 81 km 14.0 mi 0
Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).

Wildfire History

1 wildfire (100+ acres) recorded within 100 km. Largest: NEAL SMITH WUI 2016 1 (1,050 acres, 2016).

Year Name Acres Burned Distance
2016 NEAL SMITH WUI 2016 1 1,050 49 km
Source: NIFC/IRWIN Wildfire Records (100+ acres).

Monthly Weather

Month Avg Temperature Precipitation Summary
January 22°F (-6°C) 0.9 in Coldest, Driest
February 27°F (-3°C) 1.0 in
March 38°F (4°C) 2.2 in
April 51°F (10°C) 3.4 in
May 61°F (16°C) 4.3 in
June 71°F (21°C) 4.6 in Wettest
July 75°F (24°C) 4.2 in Warmest
August 73°F (23°C) 3.9 in
September 65°F (18°C) 4.0 in
October 53°F (12°C) 2.8 in
November 38°F (3°C) 2.0 in
December 26°F (-4°C) 1.2 in

St. Marys has a seasonal temperature swing of 53°F / from 22°F in January to 75°F in July. Total annual precipitation is 34.5 inches, with June being the wettest month (4.6") and January the driest (0.9").

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