Waterloo weather in May

In May, Waterloo sees average daytime highs of 70°F and overnight lows near 51°F, with 5.0 in of precipitation across 13 wet days and about 14.4 hours of daylight. It is the 5th-warmest and 2nd-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 25% 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 54 min by month's end. Set against the rest of the year, May is Waterloo's 8th-clearest and 7th-windiest month. For the whole year in context, see Waterloo's year-round climate.

Daytime high
70°
5th warmest
Overnight low
51°
8th coldest
Precipitation
5.0 in
13 wet days
Daylight
14 h 24 min
4:53 AM – 7:18 PM
Cloud cover
64%
8th clearest
Wind
10 mph
7th windiest
Solar energy
5.64 kWh/m²
Travel score
6.0
out of 10

Waterloo is city in Black Hawk County, Iowa, United States.

Density
418/km²
people per km²
Founded
1868

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 Waterloo reaches about 70°F in the afternoon and slips back to 51°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
26545
36546
46646
56647
66647
76747
86748
96748
106849
116849
126949
136950
146950
156950
167051
177051
187051
197152
207152
217152
227253
237253
247253
257354
267354
277355
287455
297455
307456
317556

How May really feels in Waterloo

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.

Waterloo weather by month

How May compares with the rest of the year at a glance. May is the 5th-warmest and 2nd-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan26° / 11°1.46.85.69.20.0
Feb31° / 15°1.46.54.810.30.0
Mar45° / 27°2.593.411.61.1
Apr59° / 39°4.311.21.113.14.3
May70° / 51°5.0130.114.46.0
Jun79° / 61°5.112.4015.16.3
Jul82° / 64°4.210.3014.86.5
Aug80° / 61°3.99.5013.76.8
Sep73° / 53°3.78.6012.37.1
Oct60° / 41°2.88.30.410.85.2
Nov45° / 29°2.17.22.19.61.2
Dec32° / 18°1.76.95.18.90.0

Cloud cover in May

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 25% of the time in May.

Beyond those clear spells, partly cloudy skies cover about 16% of May, with mostly cloudy or overcast conditions the remaining 59%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
13862
23862
33763
43862
53862
63862
73862
83862
93862
103862
113862
123862
133961
143961
153961
163961
174060
184159
194159
204258
214159
224258
234357
244357
254555
264555
274654
284555
294555
304654
314753

Chance of precipitation in May

Any precipitation

Waterloo gets around 5.0 in of rain and snow over 13 wet days in May. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable precipitation averages around 42% and peaks near 47% on the wettest days, and about 0 day brings snow. The odds climb toward the end of the month.

0%20%40%60%151015202531
Rain chance (%)
140
240
341
441
541
641
741
841
940
1040
1140
1239
1339
1439
1539
1639
1739
1840
1940
2041
2142
2242
2343
2444
2545
2645
2746
2847
2947
3047
3147

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 (%)
191720
289830
388930
487940
5861040
6841150
7841150
8821260
9811261
10801271
11801271
12781381
13781381
14771391
15761392
16761392
177513102
187313113
197313113
207114123
216914134
226815134
236615145
246516145
256316156
266217156
276018166
285819167
295620177
305520178
315321188

Wind in May

Winds average 10 mph in May.

Across May, daily wind ranges from about 9 mph on the calmest days to 10 mph at its breeziest. It stays fairly steady from day to day.

051015151015202531
Wind speed (mph)Feels
110light breeze
210light breeze
310light breeze
410light breeze
510light breeze
610light breeze
710light breeze
810light breeze
910light breeze
1010light breeze
1110light breeze
1210light breeze
1310light breeze
1410light breeze
1510light breeze
1610light breeze
1710light breeze
1810light breeze
199light breeze
209light breeze
219light breeze
229light breeze
239light breeze
249light breeze
259light breeze
269light breeze
279light breeze
289light breeze
299light breeze
309light breeze
319light breeze

Sunrise & sunset in May

DaylightNight

Daylight runs from about 13 h 48 min at the start of May to 14 h 54 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 66 minutes over May. Sunrise moves from 5:12 AM to 4:41 AM, and sunset from 7:01 PM to 7:32 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
113.85:127:01
213.95:107:03
313.95:097:04
414.05:087:05
514.05:067:06
614.05:057:07
714.15:047:08
814.15:027:09
914.25:017:10
1014.25:007:12
1114.24:597:13
1214.34:587:14
1314.34:567:15
1414.34:557:16
1514.44:547:17
1614.44:537:18
1714.44:527:19
1814.54:517:20
1914.54:507:21
2014.54:497:22
2114.64:487:23
2214.64:487:24
2314.64:477:25
2414.74:467:26
2514.74:457:27
2614.74:447:28
2714.84:447:29
2814.84:437:30
2914.84:427:31
3014.84:427:31
3114.94:417:32

Solar energy in May

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in May, about 5.64 kWh/m².

For context, solar energy here swings from a low near 1.7 kWh/m² to a high of 6.37 kWh/m² in July across the year — May's 5.64 kWh/m² sits near the top of that range.

0246151015202531
Solar energy (kWh/m²)Level
15.3Bright
25.3Bright
35.3Bright
45.3Bright
55.3Bright
65.4Bright
75.4Bright
85.4Bright
95.5Bright
105.5Bright
115.5Bright
125.6Bright
135.6Bright
145.6Bright
155.7Bright
165.7Bright
175.7Bright
185.7Bright
195.8Bright
205.8Bright
215.8Bright
225.8Bright
235.8Bright
245.8Bright
255.8Bright
265.9Bright
275.9Bright
285.9Bright
295.9Bright
306.0Bright
316.0Bright
Planning a trip in May

Is May a good time to visit Waterloo?

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

6.0
Sightseeing
5th-best month of the year
3.6
Beach & pool
5th-best month of the year

May is a reasonable time to visit Waterloo for sightseeing.

What to pack for Waterloo in May

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

In May, Waterloo sees daytime highs around 70°F and nights near 51°F. Worth packing: rain gear and sun protection. About 13 days see rain.

rain gearsun protection

UV index in Waterloo in May

LowModerateHighVery highExtreme

Clear-sky midday UV in May peaks around 7 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Waterloo peaks around June 18 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 8 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateLowJun 18UV 9Jan 1UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar4Moderate
Apr6High
May7Very high
Jun9Very high
Jul8Very high
Aug7Very high
Sep6High
Oct3Moderate
Nov2Moderate
Dec2Low

Air quality in Waterloo 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 Waterloo is worst in July — around 16 µg/m³ PM2.5 (moderate), about 2.2× the cleanest month (October, 7 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodModerateGoodJul 1916 µg/m³Oct 217 µg/m³
PM2.5 (µg/m³)Level
Jan12Moderate
Feb15Moderate
Mar14Moderate
Apr11Good
May12Good
Jun13Moderate
Jul16Moderate
Aug15Moderate
Sep12Good
Oct7Good
Nov8Good
Dec10Good
Location & terrain

Where is Waterloo?

Waterloo sits at 42.5°N, 92.3°W, 856 ft above sea level, in United States. The nearest listed city is Cedar Falls, 5.6 mi away.

Topography around Waterloo

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

Within 2 miles, the terrain around Waterloo has only modest variations in elevation — a maximum elevation change of 151 ft around an average of 873 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 243 ft; within 50 miles, only modest variations in elevation — a maximum elevation change of 620 ft.

The land around Waterloo is covered by trees (39%) and artificial surfaces (39%) within 2 miles, cropland (64%) within 10 miles, and cropland (81%) within 50 miles.

2 miles
151 ft
10 miles
243 ft
50 miles
620 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
May weather nearby: Cedar Falls 5.6 mi · Marshalltown 42 mi · Cedar Rapids 49 mi · Marion 50 mi · Mason City 63 mi · North Liberty 64 mi · Newton 66 mi · Coralville 68 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 Waterloo (42.4928°, -92.343°, elevation 856 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).