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Rock Island, Illinois climate

Dfa Hot-summer humid continental

Rock Island has a strongly seasonal cool-temperate climate (Hot-summer humid continental, Köppen Dfa). The hottest month is July with an average daily high near 84°F, while the coldest is January averaging around 13°F at night. Around 39 inches of precipitation falls each year, peaking in June (5.2 inches) and easing off in January (1.5 inches).

☀️ Summers

Warm

Highs near 84°F in July.

About 18 days a year above 90 °F

❄️ Winters

Very cold

Lows near 13°F in January.

About 115 freezing nights a year

🌧️ Rain

Moderate rainfall

About 39 in of rain a year.

Wettest in June

⛅ Sky & trend

Partly cloudy

A roughly even mix of sun and cloud.

−1.3 °F vs 50 years ago

Temperature & precipitation

Daily high–low temperature range with the monthly average, plus monthly precipitation · 1991–2020 normals · hover a month for the exact figures

Clear vs cloudy days

Share of days each month that are clear, partly cloudy or cloudy · 1991–2020 · hover a month for the day counts

Rock Island climate normals (1991–2020)

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Avg high (°F)	31	36	48	61	72	81	84	82	77	64	49	36
Avg temp (°F)	22	27	38	50	62	71	74	73	66	53	39	28
Avg low (°F)	13	18	28	39	51	61	65	63	55	43	30	20
Precipitation (in)	1.5	1.8	2.6	3.8	5.1	5.2	4.2	4.0	3.3	2.9	2.3	2.0

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Avg high (°F)	31	36	48	61	72	81
Avg temp (°F)	22	27	38	50	62	71
Avg low (°F)	13	18	28	39	51	61
Precipitation (in)	1.5	1.8	2.6	3.8	5.1	5.2

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Avg high (°F)	84	82	77	64	49	36
Avg temp (°F)	74	73	66	53	39	28
Avg low (°F)	65	63	55	43	30	20
Precipitation (in)	4.2	4.0	3.3	2.9	2.3	2.0

How often — frequency of weather events

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Days with measurable rain (days)	11	9	10	12	13	12	9	10	8	9	10	10
Days with high ≥ 90°F (days)	—	—	—	—	0.9	4	7	4	2	0.1	—	—
Days with low ≤ 32°F (days)	28	25	17	4	0.1	—	—	—	0.0	2	14	25
Days with snowfall ≥ 1 in (days)	2	1	0.5	0.1	—	—	—	—	—	0.0	0.3	0.8

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Days with measurable rain (days)	11	9	10	12	13	12
Days with high ≥ 90°F (days)	—	—	—	—	0.9	4
Days with low ≤ 32°F (days)	28	25	17	4	0.1	—
Days with snowfall ≥ 1 in (days)	2	1	0.5	0.1	—	—

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Days with measurable rain (days)	9	10	8	9	10	10
Days with high ≥ 90°F (days)	7	4	2	0.1	—	—
Days with low ≤ 32°F (days)	—	—	0.0	2	14	25
Days with snowfall ≥ 1 in (days)	—	—	—	0.0	0.3	0.8

Sky & atmosphere

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Cloud cover (%)	66	66	65	65	65	58	51	50	48	58	65	67
Clear days (≤ 30% cloud)	4	4	5	6	5	7	9	10	11	8	5	4
Partly cloudy days (30–70%)	11	10	11	9	9	10	13	12	10	9	10	10
Cloudy days (≥ 70%)	16	15	16	16	16	12	9	9	9	14	15	16
Relative humidity (%)	86	83	77	74	75	76	73	71	71	73	79	86
Wind speed (mph)	8.4	8.4	8.6	8.6	7.2	5.9	5.2	5.0	5.9	7.0	7.7	7.6

Jan – Jun	Jan	Feb	Mar	Apr	May	Jun
Cloud cover (%)	66	66	65	65	65	58
Clear days (≤ 30% cloud)	4	4	5	6	5	7
Partly cloudy days (30–70%)	11	10	11	9	9	10
Cloudy days (≥ 70%)	16	15	16	16	16	12
Relative humidity (%)	86	83	77	74	75	76
Wind speed (mph)	8.4	8.4	8.6	8.6	7.2	5.9

Jul – Dec	Jul	Aug	Sep	Oct	Nov	Dec
Cloud cover (%)	51	50	48	58	65	67
Clear days (≤ 30% cloud)	9	10	11	8	5	4
Partly cloudy days (30–70%)	13	12	10	9	10	10
Cloudy days (≥ 70%)	9	9	9	14	15	16
Relative humidity (%)	73	71	71	73	79	86
Wind speed (mph)	5.2	5.0	5.9	7.0	7.7	7.6

Methodology & sources

Temperature & precipitation — the official 1991–2020 climate normals from NOAA's U.S. Climate Normals, measured at Rock IS L&d 15 (NOAA GHCN station USC00117391), about 2 km from the city centre.

Cloud, humidity, wind & sunshine — modelled estimates from NASA POWER, NASA's satellite-and-reanalysis climatology. This is the standard global source for atmospheric variables, which are not measured at most weather stations.

How we build these numbers →