Longmont weather in August

In August, Longmont sees average daytime highs of 84°F and overnight lows near 57°F, with 1.6 in of rain across 6.8 wet days and about 13.6 hours of daylight. It is the 2nd-warmest and 7th-wettest month of the year here.

Day-to-day highs hold fairly steady near 84°F through the month. The sky is clear or mostly clear about 42% of the time in August, and the air most often feels dry.

Daylight stretches from about 14 h 12 min at the start of August to 13 hours by month's end. Set against the rest of the year, August is Longmont's 6th-clearest and 12th-windiest month. For the whole year in context, see Longmont's year-round climate.

Daytime high
84°
2nd warmest
Overnight low
57°
11th coldest
Rainfall
1.6 in
6.8 wet days
Daylight
13 h 36 min
5:16 AM – 6:53 PM
Cloud cover
49%
6th clearest
Wind
4 mph
12th windiest
Solar energy
6.48 kWh/m²
Travel score
6.1
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 August

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 84°F through the month.

A typical August day in Longmont reaches about 84°F in the afternoon and slips back to 57°F overnight — a 27°F spread between the day's warmth and the night's chill. On most days the high lands between 75°F and 92°F. Set against its neighbours, August runs about 2°F cooler than July and about 8°F warmer than September.

40°60°80°151015202531
Avg high (°F)Avg low (°F)
18559
28559
38559
48559
58558
68558
78558
88558
98558
108558
118458
128458
138458
148457
158457
168457
178457
188457
198457
208457
218457
228456
238456
248456
258356
268356
278356
288356
298355
308355
318255

How August really feels in Longmont

Once humidity and wind are folded in, August 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

August 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 August compares with the rest of the year at a glance. August is the 2nd-warmest and 7th-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 August

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 42% of the time in August.

Beyond those clear spells, partly cloudy skies cover about 25% of August, with mostly cloudy or overcast conditions the remaining 33%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
16040
26238
36238
46238
56337
66436
76535
86535
96535
106733
116733
126733
136733
146832
156832
166832
176832
186832
196832
206832
216832
226832
236832
246832
256931
266931
277030
287030
297129
307129
317228

Chance of precipitation in August

Any precipitation

Longmont gets around 1.6 in of rain over 6.8 wet days in August. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 21% and peaks near 28% on the wettest days. The odds ease toward the end of the month.

0%10%20%30%40%151015202531
Rain chance (%)
128
228
327
427
526
626
725
825
924
1024
1123
1223
1322
1422
1521
1621
1720
1820
1920
2019
2119
2219
2319
2418
2518
2617
2717
2817
2917
3017
3117

Humidity in August

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, August lands in the dry band about 78% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)
165314
264324
365314
466313
566313
667303
769292
869292
970282
1073261
1174251
1275241
1376231
1477221
1579201
1680191
1782180
1882180
1983170
2084160
2185150
2285150
2386140
2486140
2587130
2688120
2788120
2889110
2990100
3090100
319190

Wind in August

Winds average 4 mph in August, the calmest month.

Across August, daily wind ranges from about 4 mph on the calmest days to 4 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202531
Wind speed (mph)Feels
14calm
24calm
34calm
44calm
54calm
64calm
74calm
84calm
94calm
104calm
114calm
124calm
134calm
144calm
154calm
164calm
174calm
184calm
194calm
204calm
214calm
224calm
234calm
244calm
254calm
264calm
274calm
284calm
294calm
304calm
314calm

Sunrise & sunset in August

DaylightNight

Daylight runs from about 14 h 12 min at the start of August to 13 hours by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 72 minutes over August. Sunrise moves from 5:02 AM to 5:31 AM, and sunset from 7:11 PM to 6:30 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
114.25:027:11
214.15:037:10
314.15:047:09
414.15:057:08
514.05:067:07
614.05:077:05
713.95:087:04
813.95:097:03
913.95:107:02
1013.85:117:01
1113.85:126:59
1213.85:126:58
1313.75:136:57
1413.75:146:55
1513.65:156:54
1613.65:166:53
1713.65:176:51
1813.55:186:50
1913.55:196:48
2013.45:206:47
2113.45:216:45
2213.45:226:44
2313.35:236:42
2413.35:246:41
2513.25:256:39
2613.25:266:38
2713.15:276:36
2813.15:286:35
2913.15:296:33
3013.05:306:31
3113.05:316:30

Solar energy in August

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in August, about 6.48 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 — August's 6.48 kWh/m² falls in the middle.

0246151015202531
Solar energy (kWh/m²)Level
16.8Intense
26.8Intense
36.8Intense
46.7Intense
56.7Intense
66.7Intense
76.7Intense
86.7Intense
96.7Intense
106.6Intense
116.6Intense
126.6Intense
136.6Intense
146.6Intense
156.5Intense
166.5Intense
176.5Intense
186.5Intense
196.4Intense
206.4Intense
216.4Intense
226.4Intense
236.3Intense
246.3Intense
256.3Intense
266.2Intense
276.2Intense
286.2Intense
296.1Intense
306.1Intense
316.0Intense
Planning a trip in August

Is August a good time to visit Longmont?

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

6.1
Sightseeing
5th-best month of the year
7.7
Beach & pool
1st-best month of the year

August is a reasonable time to visit Longmont for sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Longmont in August

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

In August, Longmont sees daytime highs around 84°F and nights near 57°F. Pack light clothes and sun protection. About 7 days see rain.

light clothessun protection

UV index in Longmont in August

LowModerateHighVery highExtreme

Clear-sky midday UV in August peaks around 10 (very high — sun protection essential). 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 August

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where August 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
August 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).