Weather & Climate in Harmon, IL

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

Harmon experiences four distinct seasons with an average annual temperature of 49°F (10°C). Winters average 21°F in January while summers reach 74°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 40.5 inches. The area receives 31.2 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 676 feet.

Temperature

21°F Jan (-6°C) 74°F Jul (23°C)

Annual Average	49.4°F
	9% below US avg
January Average	21°F (-6°C)
July Average	74°F (23°C)
Sunny Days	275 days/yr

Geography

Elevation	676 ft (206 m)
Area	0.1 sq mi (0.2 km²)
Population Density	368/sq mi
Coordinates	41.7235°N, 89.5539°W
Timezone	America/Chicago
County	Lee County County
Nearest Airport	Illinois Valley Regional-Walter A Duncan Field (VYS) 33 miles away

Precipitation & Snow

Annual Rainfall 40.5"

7% above US avg

Snowfall 31.2"

Wettest Month (Jun) 4.69"

Driest Month (Feb) 1.34"

Air Quality

AQI Median	43.0
Rating	Good

Natural Hazard Risk

Overall Risk	Relatively Low
Risk Score	54.4 / 100
Social Vulnerability	23.2 / 100
Community Resilience	82.7 / 100

Hazard Breakdown

Tornado	Relatively Moderate
Hurricane	Very Low
Earthquake	Very Low
Wildfire	Very Low
Flood	Relatively Low
Hail	Relatively Low
Strong Wind	Relatively High
Heat Wave	Very Low
Winter Weather	Relatively Low
Lightning	Relatively Low
Ice Storm	Relatively Low
Drought	Relatively Moderate
Cold Wave	Relatively Moderate
Landslide	Very Low

Source: FEMA National Risk Index v1.20 (Dec 2025)

Earthquake History

8 earthquakes (M2.5+) recorded within 150 km since 1990. Strongest on record: M4.2.

Jun 28, 2004	12 km NW of Dayton, Illinois	M4.2	62 km	10 km
Feb 10, 2010	2 km NW of Lily Lake, Illinois	M3.8	92 km	10 km
Sep 2, 1999	8 km W of Amboy, Illinois	M3.5	10 km	5 km
Nov 4, 2013	1 km SSW of Lyons, Illinois	M3.2	144 km	1 km
Jul 15, 2024	2 km WNW of Somonauk, Illinois	M3.1	71 km	10 km
Mar 25, 2015	3 km WNW of Lake in the Hills, Illinois	M2.9	111 km	6 km
Jun 10, 2013	4 km NNE of Virgil, Illinois	M2.6	92 km	5 km
Mar 15, 2025	6 km W of Dwight, Illinois	M2.6	113 km	5 km

Source: USGS Earthquake Catalog (M2.5+, 1990–2025). Sorted by magnitude.

Tornado History

594 tornadoes (EF0+) recorded within 100 km since 1950. Strongest on record: EF4. Total: 43 fatalities, 796 injuries.

Date	Rating	Distance	Path	Fatalities
Apr 9, 2015	EF4	26 km	30.1 mi	2
Mar 29, 1981	EF4	33 km	5.1 mi	0
Apr 21, 1967	EF4	76 km	25.5 mi	24
Feb 28, 2017	EF3	92 km	17.8 mi	0
Feb 28, 2017	EF3	67 km	11.5 mi	2
Jun 5, 2010	EF3	98 km	8.6 mi	0
Jan 7, 2008	EF3	95 km	13.2 mi	0
Apr 20, 2004	EF3	57 km	15.8 mi	8
May 9, 1995	EF3	51 km	22.0 mi	0
Mar 13, 1990	EF3	62 km	15.5 mi	0
Aug 5, 1979	EF3	33 km	5.7 mi	0
Jun 30, 1977	EF3	49 km	6.1 mi	0
Mar 4, 1976	EF3	58 km	0.8 mi	0
Jun 20, 1974	EF3	66 km	10.6 mi	1
May 13, 1974	EF3	88 km	3.6 mi	0
Jul 17, 1972	EF3	73 km	81.5 mi	0
Apr 16, 1967	EF3	94 km	27.8 mi	0
Jan 24, 1967	EF3	99 km	24.9 mi	0
Jan 24, 1967	EF3	54 km	7.4 mi	0
Apr 19, 1966	EF3	83 km	2.0 mi	0

Source: NOAA Storm Prediction Center (EF0+, 1950–2024, US only).

Monthly Weather

Month	Avg Temperature	Precipitation	Summary
January	21°F (-6°C)	1.4 in	Coldest
February	25°F (-4°C)	1.3 in	Driest
March	36°F (2°C)	2.6 in
April	49°F (9°C)	3.6 in
May	61°F (16°C)	4.5 in
June	70°F (21°C)	4.7 in	Wettest
July	74°F (23°C)	3.6 in	Warmest
August	71°F (22°C)	4.3 in
September	64°F (18°C)	3.6 in
October	52°F (11°C)	2.8 in
November	38°F (3°C)	2.7 in
December	25°F (-4°C)	2.1 in

Harmon has a seasonal temperature swing of 52°F / from 21°F in January to 74°F in July. Total annual precipitation is 37.1 inches, with June being the wettest month (4.7") and February the driest (1.3").

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