Longmont weather in May

In May, Longmont sees average daytime highs of 69°F and overnight lows near 44°F, with 3.4 in of precipitation across 11.7 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 65°F in the first days to 74°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 Longmont's 12th-clearest and 3rd-windiest month. For the whole year in context, see Longmont's year-round climate.

Daytime high
69°
5th warmest
Overnight low
44°
8th coldest
Precipitation
3.4 in
11.7 wet days
Daylight
14 h 12 min
4:50 AM – 7:03 PM
Cloud cover
61%
12th clearest
Wind
5 mph
3rd windiest
Solar energy
6.72 kWh/m²
Travel score
6.2
out of 10

Longmont is city in Boulder County, Colorado, United States.

Density
1,228/km²
people per km²
Founded
1871

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 Longmont reaches about 69°F in the afternoon and slips back to 44°F overnight — a 26°F spread between the day's warmth and the night's chill. On most days the high lands between 55°F and 83°F. Set against its neighbours, May runs about 9°F warmer than April and about 11°F cooler than June.

20°40°60°80°151015202531
Avg high (°F)Avg low (°F)
16438
26439
36539
46540
56540
66640
76640
86741
96741
106742
116842
126842
136943
146943
156943
166944
177044
187044
197045
207145
217145
227146
237246
247246
257247
267347
277347
287348
297448
307448
317449

How May really feels in Longmont

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.

Longmont 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
Jan41° / 18°0.84.74.59.50.1
Feb44° / 20°0.85.3510.41.0
Mar54° / 27°1.67.34.411.73.6
Apr61° / 35°2.69.54135.0
May69° / 44°3.411.70.614.26.2
Jun80° / 53°2.18.5014.86.6
Jul86° / 59°1.77.4014.65.3
Aug84° / 57°1.66.8013.66.1
Sep76° / 49°1.55.90.412.37.6
Oct63° / 37°1.66.51.910.96.2
Nov50° / 27°1.15.84.49.82.7
Dec41° / 19°0.74.54.49.20.2

Cloud cover in May

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 24% of the time in May, the cloudiest month of the year.

Beyond those clear spells, partly cloudy skies cover about 24% of May, with mostly cloudy or overcast conditions the remaining 52%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
14951
24951
35050
45050
55050
65050
75149
85149
95050
105050
115050
125050
134951
144852
154852
164852
174753
184753
194654
204654
214654
224654
234654
244654
254654
264753
274852
284951
295050
305248
315248

Chance of precipitation in May

Any precipitationSnow

Longmont gets around 3.4 in of rain and snow over 11.7 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 precipitation averages around 38% and peaks near 41% on the wettest days, and about 1 day brings snow.

0%10%20%30%40%50%151015202531
Rain chance (%)Snow chance (%)
1378
2378
3377
4377
5366
6365
7365
8354
9354
10353
11353
12363
13363
14362
15372
16382
17382
18392
19391
20401
21401
22401
23411
24411
25411
26410
27410
28410
29400
30400
31390

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 100% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)
11000
21000
31000
41000
51000
61000
71000
81000
91000
101000
111000
121000
131000
141000
151000
161000
171000
181000
191000
201000
211000
221000
231000
241000
25991
26991
27991
28991
29991
30982
31982

Wind in May

Winds average 5 mph in May.

Across May, daily wind ranges from about 5 mph on the calmest days to 5 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202531
Wind speed (mph)Feels
15calm
25calm
35calm
45calm
55calm
65calm
75calm
85calm
95calm
105calm
115calm
125calm
135calm
145calm
155calm
165calm
175calm
185calm
195calm
205calm
215calm
225calm
235calm
245calm
255calm
265calm
275calm
285calm
295calm
305calm
315calm

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 5:07 AM to 4:39 AM, and sunset from 6:48 PM to 7:16 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
113.75:076:48
213.75:066:49
313.85:056:50
413.85:036:51
513.85:026:52
613.95:016:53
713.95:006:54
813.94:596:55
914.04:576:56
1014.04:566:57
1114.14:556:58
1214.14:546:59
1314.14:537:00
1414.24:527:01
1514.24:517:02
1614.24:507:03
1714.24:497:04
1814.34:487:05
1914.34:477:06
2014.34:477:07
2114.44:467:08
2214.44:457:09
2314.44:447:10
2414.54:447:11
2514.54:437:11
2614.54:427:12
2714.54:427:13
2814.64:417:14
2914.64:407:15
3014.64:407:16
3114.64:397:16

Solar energy in May

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in May, about 6.72 kWh/m².

For context, solar energy here swings from a low near 2.42 kWh/m² to a high of 7.36 kWh/m² in June across the year — May's 6.72 kWh/m² sits near the top of that range.

02468151015202531
Solar energy (kWh/m²)Level
16.5Intense
26.5Intense
36.5Intense
46.5Intense
56.6Intense
66.6Intense
76.6Intense
86.6Intense
96.6Intense
106.7Intense
116.7Intense
126.7Intense
136.7Intense
146.7Intense
156.7Intense
166.7Intense
176.7Intense
186.7Intense
196.8Intense
206.8Intense
216.8Intense
226.8Intense
236.8Intense
246.8Intense
256.8Intense
266.9Intense
276.9Intense
286.9Intense
297.0Intense
307.0Intense
317.0Intense
Planning a trip in May

Is May a good time to visit Longmont?

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

6.2
Sightseeing
3rd-best month of the year
3.6
Beach & pool
5th-best month of the year

May is a reasonable time to visit Longmont for sightseeing.

What to pack for Longmont in May

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

In May, Longmont sees daytime highs around 69°F and nights near 44°F. Pack sun protection. Worth having: a warm layer and rain gear. About 12 days see rain.

sun protectiona warm layerrain gear

UV index in Longmont 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 Longmont peaks around July 13 at about 11 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 23 at about 2 (moderate).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 10 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highExtremeVery highHighModerateJul 13UV 11Dec 23UV 2
UV index (midday)Level
Jan2Moderate
Feb4Moderate
Mar7High
Apr6High
May7Very high
Jun11Extreme
Jul11Extreme
Aug10Very high
Sep7Very high
Oct5High
Nov3Moderate
Dec2Low

Air quality in Longmont 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 Longmont is worst in October — around 30 µg/m³ PM2.5 (moderate), about 3.1× the cleanest month (November, 10 µg/m³).

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

010203040JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodModerateGoodOct 1528 µg/m³Nov 2310 µg/m³
PM2.5 (µg/m³)Level
Jan12Good
Feb12Moderate
Mar14Moderate
Apr11Good
May11Good
Jun12Good
Jul14Moderate
Aug19Moderate
Sep17Moderate
Oct30Moderate
Nov10Good
Dec11Good
Location & terrain

Where is Longmont?

Longmont sits at 40.2°N, 105.1°W, 4,984 ft above sea level, in United States. The nearest listed city is Erie, 8.7 mi away.

Topography around Longmont

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

Within 2 miles, the terrain around Longmont has only modest variations in elevation — a maximum elevation change of 197 ft around an average of 4,993 ft above sea level; within 10 miles, significant variations in elevation — a maximum elevation change of 1,765 ft; within 50 miles, extreme variations in elevation — a maximum elevation change of 9,721 ft.

The land around Longmont is covered by artificial surfaces (50%) and trees (22%) within 2 miles, grassland (54%) and cropland (25%) within 10 miles, and grassland (42%) and trees (31%) within 50 miles.

2 miles
197 ft
10 miles
1,765 ft
50 miles
9,721 ft
treesgrasslandcroplandartificial surfacesbare terrainwatermoss and lichen
May weather nearby: Erie 8.7 mi · Lafayette 12 mi · Louisville 13 mi · Boulder 14 mi · Loveland 16 mi · Broomfield 17 mi · Brighton 19 mi · Northglenn 21 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 Longmont (40.1672°, -105.1019°, elevation 4,984 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).