Decatur weather in May

In May, Decatur sees average daytime highs of 73°F and overnight lows near 55°F, with 4.8 in of rain across 13.2 wet days and about 14.2 hours of daylight. It is the 5th-warmest and 1st-wettest month of the year here.

Highs climb over the month, from about 69°F in the first days to 77°F by the end. The sky is clear or mostly clear about 24% of the time in May, and the air most often feels dry.

Daylight stretches from about 13 h 42 min at the start of May to 14 h 36 min by month's end. Set against the rest of the year, May is Decatur's 8th-clearest and 8th-windiest month. For the whole year in context, see Decatur's year-round climate.

Daytime high
73°
5th warmest
Overnight low
55°
8th coldest
Rainfall
4.8 in
13.2 wet days
Daylight
14 h 12 min
4:46 AM – 6:58 PM
Cloud cover
64%
8th clearest
Wind
9 mph
8th windiest
Solar energy
5.8 kWh/m²
Travel score
6.2
out of 10

Decatur is city in Macon County, Illinois, United States.

Density
602/km²
people per km²
Founded
1823

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 69°F in the first days to 77°F by the end.

A typical May day in Decatur reaches about 73°F in the afternoon and slips back to 55°F overnight — a 18°F spread between the day's warmth and the night's chill. On most days the high lands between 61°F and 84°F. Set against its neighbours, May runs about 10°F warmer than April and about 8°F cooler than June.

40°60°80°151015202531
Avg high (°F)Avg low (°F)
16950
26950
36951
47051
57051
67052
77152
87153
97153
107253
117253
127254
137354
147354
157355
167355
177455
187456
197456
207456
217557
227557
237557
247658
257658
267658
277759
287759
297760
307860
317860

How May really feels in Decatur

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.

Decatur 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
Jan36° / 21°2.78.549.50.0
Feb40° / 24°2.37.53.410.40.2
Mar52° / 34°3.39.71.511.72.7
Apr64° / 44°4.611.80.3135.3
May73° / 55°4.813.2014.26.2
Jun82° / 64°4.310.9014.86.0
Jul84° / 67°3.610.3014.55.5
Aug83° / 65°3.08.5013.66.1
Sep78° / 57°3.27.4012.37.3
Oct65° / 46°3.58.60.110.96.2
Nov51° / 35°3.58.70.89.82.7
Dec40° / 26°2.58.72.99.20.2

Cloud cover in May

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 24% of the time in May.

Beyond those clear spells, partly cloudy skies cover about 17% of May, with mostly cloudy or overcast conditions the remaining 59%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
14060
24060
34159
44159
54060
64060
74258
84258
94159
104159
114258
124258
134159
144258
154258
164258
174258
184159
194159
204159
214258
224258
234258
244258
254258
264258
274258
284258
294258
304357
314357

Chance of precipitation in May

Any precipitation

Decatur gets around 4.8 in of rain over 13.2 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 44% on the wettest days.

0%10%20%30%40%50%151015202531
Rain chance (%)
143
243
342
442
542
642
742
842
942
1042
1142
1242
1342
1442
1543
1643
1743
1843
1944
2044
2144
2243
2343
2443
2543
2642
2742
2842
2941
3040
3140

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 56% of days. Sticky, muggy-or-worse air turns up on roughly 11% of them.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
17814620
27615720
37416820
47217830
57117930
668181040
767181140
866181150
964191250
1062191360
1161191460
1260191470
1358191580
1459181580
1557181690
1657181690
17561816100
18541817110
19531817120
20521818120
21511718131
22491719141
23481719151
24461820161
25451820161
26441820171
27421821181
28411921181
29401921192
30391921202
31372021202

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
188light breeze
198light breeze
208light breeze
218light 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 42 min at the start of May to 14 h 36 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 54 minutes over May. Sunrise moves from 5:03 AM to 4:36 AM, and sunset from 6:43 PM to 7:11 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
113.75:036:43
213.75:026:44
313.75:016:45
413.84:596:46
513.84:586:47
613.84:576:48
713.94:566:49
813.94:556:50
914.04:546:51
1014.04:526:52
1114.04:516:53
1214.14:506:54
1314.14:496:55
1414.14:486:56
1514.24:476:57
1614.24:466:58
1714.24:456:59
1814.34:457:00
1914.34:447:01
2014.34:437:02
2114.34:427:02
2214.44:417:03
2314.44:417:04
2414.44:407:05
2514.44:397:06
2614.54:387:07
2714.54:387:08
2814.54:377:08
2914.54:377:09
3014.64:367:10
3114.64:367:11

Solar energy in May

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in May, about 5.8 kWh/m².

For context, solar energy here swings from a low near 1.8 kWh/m² to a high of 6.44 kWh/m² in June across the year — May's 5.8 kWh/m² sits near the top of that range.

0246151015202531
Solar energy (kWh/m²)Level
15.4Bright
25.4Bright
35.4Bright
45.5Bright
55.5Bright
65.5Bright
75.6Bright
85.6Bright
95.6Bright
105.7Bright
115.7Bright
125.7Bright
135.8Bright
145.8Bright
155.8Bright
165.8Bright
175.8Bright
185.9Bright
195.9Bright
205.9Bright
215.9Bright
226.0Bright
236.0Bright
246.0Bright
256.0Intense
266.0Intense
276.0Intense
286.0Intense
296.1Intense
306.1Intense
316.1Intense
Planning a trip in May

Hazard calendar for Decatur

In seasonPeak

None of Decatur's seasonal hazards are active in May. The full-year calendar below shows when the rainy season, cyclone risk and dust haze do peak.

Decatur sits in the Atlantic hurricane belt; the season peaks August–October.

Atlantic hurricane
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is May a good time to visit Decatur?

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

6.2
Sightseeing
2nd-best month of the year
4.8
Beach & pool
5th-best month of the year

May is a reasonable time to visit Decatur for sightseeing.

What to pack for Decatur in May

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

In May, Decatur sees daytime highs around 73°F and nights near 55°F. Worth packing: light clothes, rain gear and sun protection. About 13 days see rain.

light clothesrain gearsun protection

UV index in Decatur 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 Decatur peaks around June 22 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near January 1 at about 2 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 9 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateJun 22UV 9Jan 1UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr6High
May8Very high
Jun9Very high
Jul9Very high
Aug8Very high
Sep6High
Oct4Moderate
Nov3Moderate
Dec2Low

Air quality in Decatur 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 Decatur is worst in July — around 17 µg/m³ PM2.5 (moderate), about 2.1× the cleanest month (October, 8 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodModerateGoodJul 1716 µg/m³Oct 228 µg/m³
PM2.5 (µg/m³)Level
Jan10Good
Feb13Moderate
Mar12Moderate
Apr11Good
May14Moderate
Jun14Moderate
Jul17Moderate
Aug15Moderate
Sep12Good
Oct8Good
Nov8Good
Dec9Good
Location & terrain

Where is Decatur?

Decatur sits at 39.8°N, 89.0°W, 673 ft above sea level, in United States. The nearest listed city is Springfield, 37 mi away.

Topography around Decatur

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

Within 2 miles, the terrain around Decatur has only modest variations in elevation — a maximum elevation change of 164 ft around an average of 666 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 197 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 489 ft.

The land around Decatur is covered by trees (43%) and artificial surfaces (34%) within 2 miles, cropland (68%) within 10 miles, and cropland (83%) within 50 miles.

2 miles
164 ft
10 miles
197 ft
50 miles
489 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
May weather nearby: Springfield 37 mi · Mattoon 40 mi · Champaign 42 mi · Urbana 43 mi · Bloomington 45 mi · Normal 47 mi · Charleston 48 mi · Morton 60 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 Decatur (39.8403°, -88.9548°, elevation 673 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. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). 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).