DeKalb weather in May

In May, DeKalb sees average daytime highs of 69°F and overnight lows near 50°F, with 4.8 in of rain across 12.8 wet days and about 14.3 hours of daylight. It is the 5th-warmest and 1st-wettest month of the year here.

Highs climb over the month, from about 65°F in the first days to 74°F by the end. The sky is clear or mostly clear about 26% of the time in May, and the air most often feels dry.

Daylight stretches from about 13 h 48 min at the start of May to 14 h 48 min by month's end. Set against the rest of the year, May is DeKalb's 7th-clearest and 8th-windiest month. For the whole year in context, see DeKalb's year-round climate.

Daytime high
69°
5th warmest
Overnight low
50°
8th coldest
Rainfall
4.8 in
12.8 wet days
Daylight
14 h 24 min
4:40 AM – 7:02 PM
Cloud cover
65%
7th clearest
Wind
9 mph
8th windiest
Solar energy
5.69 kWh/m²
Travel score
5.9
out of 10

DeKalb is city in De Kalb County, Illinois, United States.

Density
1,080/km²
people per km²
Founded
1837

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in May

Average highAverage lowShaded bands: 10–90% of days

Highs climb over the month, from about 65°F in the first days to 74°F by the end.

A typical May day in DeKalb reaches about 69°F in the afternoon and slips back to 50°F overnight — a 19°F spread between the day's warmth and the night's chill. On most days the high lands between 57°F and 82°F. Set against its neighbours, May runs about 11°F warmer than April and about 9°F cooler than June.

40°60°80°151015202531
Avg high (°F)Avg low (°F)
16445
26446
36546
46546
56547
66647
76647
86748
96748
106748
116849
126849
136849
146949
156950
166950
177050
187051
197051
207151
217152
227152
237253
247253
257253
267354
277354
287354
297455
307455
317455

How May really feels in DeKalb

Once humidity and wind are folded in, May averages 0 days that feel above 90°F and 0 that feel at or below 32°F — the comfort signal a plain temperature reading hides.

Days feeling ≥ 90°F
0
heat index over the day's high
Days feeling ≤ 32°F
0
wind chill below the day's low

May sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

DeKalb weather by month

How May compares with the rest of the year at a glance. May is the 5th-warmest and 1st-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan29° / 16°2.07.65.79.30.0
Feb34° / 19°1.86.94.910.30.0
Mar46° / 29°2.69.32.911.71.3
Apr59° / 40°4.4120.913.14.1
May69° / 50°4.812.8014.35.9
Jun78° / 60°4.212.20156.3
Jul82° / 64°3.510.7014.76.4
Aug80° / 62°3.510.4013.76.6
Sep74° / 54°3.28.7012.37.0
Oct61° / 43°3.19.10.110.95.2
Nov47° / 32°2.47.71.69.61.5
Dec35° / 22°2.27.84.590.0

Cloud cover in May

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 26% of the time in May.

Beyond those clear spells, partly cloudy skies cover about 13% of May, with mostly cloudy or overcast conditions the remaining 61%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
13565
23565
33565
43565
53565
63664
73664
83763
93763
103862
113961
123961
133961
144060
154159
164159
174159
184159
194060
204060
214159
224159
234159
244060
254060
264159
274159
284060
294060
304258
314258

Chance of precipitation in May

Any precipitation

DeKalb gets around 4.8 in of rain over 12.8 wet days in May, the wettest month. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 42% and peaks near 43% on the wettest days.

0%10%20%30%40%50%151015202531
Rain chance (%)
142
242
343
443
543
643
743
843
943
1042
1142
1242
1342
1441
1541
1641
1741
1841
1941
2041
2141
2241
2341
2441
2541
2641
2741
2841
2941
3041
3141

Humidity in May

DryComfortableHumidMuggyOppressiveMiserable

Most of May feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, May lands in the dry band about 74% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
1898210
2898210
3889210
4879310
58610310
68510410
78311420
88311420
98211520
108112520
118012530
127912630
137813630
147713730
157613740
167514740
177414840
187314850
197215850
207015960
216916960
2267161070
2367161070
2464171180
2563171280
2662171290
2761171390
2860181390
29581814100
30571814101
31551915101

Wind in May

Winds average 9 mph in May.

Across May, daily wind ranges from about 8 mph on the calmest days to 9 mph at its breeziest. It stays fairly steady from day to day.

051015151015202531
Wind speed (mph)Feels
19light breeze
29light breeze
39light breeze
49light breeze
59light breeze
69light breeze
79light breeze
89light breeze
99light breeze
109light breeze
119light breeze
129light breeze
139light breeze
149light breeze
159light breeze
169light breeze
179light breeze
189light breeze
199light breeze
209light breeze
219light breeze
228light breeze
238light breeze
248light breeze
258light breeze
268light breeze
278light breeze
288light breeze
298light breeze
308light breeze
318light breeze

Sunrise & sunset in May

DaylightNight

Daylight runs from about 13 h 48 min at the start of May to 14 h 48 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 60 minutes over May. Sunrise moves from 4:58 AM to 4:29 AM, and sunset from 6:46 PM to 7:16 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
113.84:586:46
213.84:576:47
313.94:566:48
413.94:546:49
514.04:536:50
614.04:526:51
714.04:516:53
814.14:496:54
914.14:486:55
1014.14:476:56
1114.24:466:57
1214.24:456:58
1314.34:446:59
1414.34:427:00
1514.34:417:01
1614.44:407:02
1714.44:397:03
1814.44:387:04
1914.54:377:05
2014.54:377:06
2114.54:367:07
2214.64:357:08
2314.64:347:09
2414.64:337:10
2514.64:327:11
2614.74:327:12
2714.74:317:13
2814.74:307:14
2914.74:307:15
3014.84:297:15
3114.84:297:16

Solar energy in May

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in May, about 5.69 kWh/m².

For context, solar energy here swings from a low near 1.69 kWh/m² to a high of 6.29 kWh/m² in June across the year — May's 5.69 kWh/m² sits near the top of that range.

0246151015202531
Solar energy (kWh/m²)Level
15.3Bright
25.3Bright
35.3Bright
45.4Bright
55.4Bright
65.4Bright
75.4Bright
85.5Bright
95.5Bright
105.5Bright
115.6Bright
125.6Bright
135.6Bright
145.7Bright
155.7Bright
165.7Bright
175.8Bright
185.8Bright
195.8Bright
205.8Bright
215.8Bright
225.9Bright
235.9Bright
245.9Bright
255.9Bright
265.9Bright
275.9Bright
286.0Bright
296.0Bright
306.0Bright
316.0Bright
Planning a trip in May

Is May a good time to visit DeKalb?

Our two travel scores rate May for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

5.9
Sightseeing
5th-best month of the year
3.5
Beach & pool
5th-best month of the year

May is a reasonable time to visit DeKalb for sightseeing.

What to pack for DeKalb in May

From May's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In May, DeKalb sees daytime highs around 69°F and nights near 50°F. Worth packing: rain gear and sun protection. About 13 days see rain.

rain gearsun protection

UV index in DeKalb in May

LowModerateHighVery highExtreme

Clear-sky midday UV in May peaks around 8 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in DeKalb peaks around June 19 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 19 at about 2 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 8 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateLowJun 19UV 9Dec 19UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar4Moderate
Apr6High
May8Very high
Jun9Very high
Jul8Very high
Aug8Very high
Sep6High
Oct3Moderate
Nov2Moderate
Dec2Low

Air quality in DeKalb in May

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where May falls, not just the annual average.

Air quality in DeKalb is worst in July — around 17 µg/m³ PM2.5 (moderate), about 1.9× the cleanest month (October, 9 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

01020JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodJul 1817 µg/m³Oct 229 µg/m³
PM2.5 (µg/m³)Level
Jan12Moderate
Feb15Moderate
Mar16Moderate
Apr14Moderate
May15Moderate
Jun16Moderate
Jul17Moderate
Aug16Moderate
Sep13Moderate
Oct9Good
Nov10Good
Dec11Good
Location & terrain

Where is DeKalb?

DeKalb sits at 41.9°N, 88.8°W, 879 ft above sea level, in United States. The nearest listed city is Sycamore, 5.0 mi away.

Topography around DeKalb

How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of DeKalb.

Within 2 miles, the terrain around DeKalb has only modest variations in elevation — a maximum elevation change of 102 ft around an average of 883 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 308 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 850 ft.

The land around DeKalb is covered by artificial surfaces (35%), trees (23%) and grassland (23%) within 2 miles, cropland (84%) within 10 miles, and cropland (59%) within 50 miles.

2 miles
102 ft
10 miles
308 ft
50 miles
850 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
May weather nearby: Sycamore 5.0 mi · Wasco 18 mi · St. Charles 23 mi · Geneva 23 mi · Batavia 23 mi · Huntley 24 mi · North Aurora 24 mi · Belvidere 24 mi

United States travel facts

Power plugs
Type A / B
120 V · 60 Hz
Prices
≈ 100% of US
price level, 2025
GDP per capita
$90,027
2025
Happiness
6.8 / 10
World Happiness, 2025
Safe drinking water
98%
of population, 2024
Homicide rate
5.8
per 100k, 2023
Road deaths
12.7
per 100k/yr, 2019
Income group
High
World Bank
Religion
Protestant 47%unaffiliated 23%Roman Catholic 21%Jewish 2%

Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.

Data sources

Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for DeKalb (41.9295°, -88.7504°, elevation 879 ft), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).