Portsmouth weather in August

In August, Portsmouth sees average daytime highs of 74°F and overnight lows near 64°F, with 3.2 in of rain across 8.8 wet days and about 13.8 hours of daylight. It is the 2nd-warmest and 11th-wettest month of the year here.

Day-to-day highs hold fairly steady near 74°F through the month. The sky is clear or mostly clear about 36% of the time in August, and the air most often feels humid.

Daylight stretches from about 14 h 24 min at the start of August to 13 h 06 min by month's end. Set against the rest of the year, August is Portsmouth's 2nd-clearest and 12th-windiest month. For the whole year in context, see Portsmouth's year-round climate.

Daytime high
74°
2nd warmest
Overnight low
64°
11th coldest
Rainfall
3.2 in
8.8 wet days
Daylight
13 h 48 min
4:54 AM – 6:40 PM
Cloud cover
54%
2nd clearest
Wind
8 mph
12th windiest
Solar energy
5.43 kWh/m²
Travel score
7.2
out of 10

Portsmouth is city in Rockingham County, New Hampshire, United States.

Density
494/km²
people per km²
Founded
1630

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 74°F through the month.

A typical August day in Portsmouth reaches about 74°F in the afternoon and slips back to 64°F overnight — a 11°F spread between the day's warmth and the night's chill. On most days the high lands between 68°F and 81°F. Set against its neighbours, August runs on par with July and about 6°F warmer than September.

50°60°70°80°151015202531
Avg high (°F)Avg low (°F)
17665
27665
37665
47665
57665
67565
77565
87565
97565
107565
117565
127565
137564
147564
157564
167564
177464
187464
197464
207464
217464
227463
237463
247463
257463
267463
277362
287362
297362
307362
317362

How August really feels in Portsmouth

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.

Portsmouth weather by month

How August compares with the rest of the year at a glance. August is the 2nd-warmest and 11th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan34° / 22°3.69.96.79.20.0
Feb35° / 23°3.49.1610.20.0
Mar41° / 30°4.511.25.211.60.2
Apr51° / 40°4.210.61.313.12.4
May60° / 49°3.310.5014.44.7
Jun69° / 58°3.610.6015.16.3
Jul75° / 65°3.110.6014.96.9
Aug74° / 64°3.28.8013.87.2
Sep68° / 57°3.48.5012.36.6
Oct58° / 47°4.49.90.210.84.5
Nov48° / 37°3.89.71.29.51.8
Dec39° / 28°4.610.84.98.90.1

Cloud cover in August

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 36% of the time in August.

Beyond those clear spells, partly cloudy skies cover about 19% of August, with mostly cloudy or overcast conditions the remaining 45%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
15545
25545
35545
45545
55446
65446
75446
85347
95248
105248
115248
125248
135248
145248
155248
165248
175248
185446
195446
205545
215545
225743
235842
245842
255842
265941
275941
285941
295941
305941
315842

Chance of precipitation in August

Any precipitation

Portsmouth gets around 3.2 in of rain over 8.8 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 29% and peaks near 33% on the wettest days. The odds ease toward the end of the month.

0%10%20%30%40%151015202531
Rain chance (%)
133
233
332
432
531
631
731
831
931
1030
1130
1230
1330
1430
1530
1629
1729
1829
1928
2028
2127
2227
2327
2426
2526
2626
2726
2825
2925
3026
3126

Humidity in August

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, August lands in the humid band about 35% of days. Sticky, muggy-or-worse air turns up on roughly 29% of them.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
162233335
262333335
362334335
462334325
562335325
672235314
772236314
872236314
972237304
1072237304
1182237293
1282238293
1392338283
1492338273
1592338273
16102338263
17102438262
18112438252
19122437252
20122536242
21132636242
22142635232
23152734222
24162833212
25172932212
26182931202
27193030192
28203029182
29213129181
30223128171
31243127171

Wind in August

Winds average 8 mph in August, the calmest month.

Across August, daily wind ranges from about 7 mph on the calmest days to 8 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202531
Wind speed (mph)Feels
17calm
27calm
37calm
47calm
57calm
67calm
77calm
87calm
97calm
107calm
117light breeze
127light breeze
137light breeze
147light breeze
158light breeze
168light breeze
178light 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 August

DaylightNight

Daylight runs from about 14 h 24 min at the start of August to 13 h 06 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 78 minutes over August. Sunrise moves from 4:37 AM to 5:11 AM, and sunset from 7:01 PM to 6:15 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
114.44:377:01
214.44:387:00
314.34:396:58
414.34:416:57
514.24:426:56
614.24:436:55
714.24:446:53
814.14:456:52
914.14:466:51
1014.04:476:49
1114.04:486:48
1214.04:496:46
1313.94:506:45
1413.94:526:44
1513.84:536:42
1613.84:546:40
1713.74:556:39
1813.74:566:37
1913.64:576:36
2013.64:586:34
2113.64:596:33
2213.55:016:31
2313.55:026:29
2413.45:036:28
2513.45:046:26
2613.35:056:24
2713.35:066:22
2813.25:076:21
2913.25:086:19
3013.15:106:17
3113.15:116:15

Solar energy in August

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in August, about 5.43 kWh/m².

For context, solar energy here swings from a low near 1.54 kWh/m² to a high of 6.11 kWh/m² in July across the year — August's 5.43 kWh/m² falls in the middle.

0246151015202531
Solar energy (kWh/m²)Level
15.8Bright
25.7Bright
35.7Bright
45.7Bright
55.7Bright
65.6Bright
75.6Bright
85.6Bright
95.5Bright
105.5Bright
115.5Bright
125.5Bright
135.4Bright
145.4Bright
155.4Bright
165.4Bright
175.4Bright
185.3Bright
195.3Bright
205.3Bright
215.3Bright
225.3Bright
235.3Bright
245.2Bright
255.2Bright
265.2Bright
275.2Bright
285.1Bright
295.1Bright
305.0Bright
315.0Bright
Planning a trip in August

Hazard calendar for Portsmouth

In seasonPeak

In August, Portsmouth sits inside its atlantic hurricane season. The full year is below, with each hazard's peak months called out.

Portsmouth 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 August a good time to visit Portsmouth?

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

7.2
Sightseeing
1st-best month of the year
5.8
Beach & pool
2nd-best month of the year

August is one of the better times to visit Portsmouth for general sightseeing.

What to pack for Portsmouth in August

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

In August, Portsmouth sees daytime highs around 74°F and nights near 64°F. Worth packing: light clothes, rain gear and sun protection. About 9 days see rain.

light clothesrain gearsun protection

Sea temperature near Portsmouth in August

The nearest coast averages about 65°F in August — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea offshore is warmest in August at about 65°F and coldest in March near 38°F.

The water stays below 68°F all year — cool enough that most swimmers want a wetsuit.

40°50°60°70°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshing
Sea temperature (°F)Comfort
Jan42Bracing
Feb39Bracing
Mar38Bracing
Apr42Bracing
May49Bracing
Jun57Bracing
Jul63Cool
Aug65Cool
Sep62Cool
Oct55Bracing
Nov49Bracing
Dec45Bracing

UV index in Portsmouth in August

LowModerateHighVery highExtreme

Clear-sky midday UV in August peaks around 4 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Portsmouth peaks around July 10 at about 7 (very high) — sunscreen and a hat are worth it in the middle of the day. It bottoms out near December 23 at about 1 (low).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighHighModerateModerateLowJul 10UV 7Dec 23UV 1
UV index (midday)Level
Jan1Low
Feb2Moderate
Mar4Moderate
Apr5High
May7High
Jun7High
Jul7Very high
Aug4Moderate
Sep6High
Oct3Moderate
Nov2Moderate
Dec1Low
Location & terrain

Where is Portsmouth?

Portsmouth sits at 43.1°N, 70.8°W, 20 ft above sea level, in United States. The nearest listed city is Dover, 9.9 mi away.

Topography around Portsmouth

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

Within 2 miles, the terrain around Portsmouth has only modest variations in elevation — a maximum elevation change of 161 ft around an average of 39 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 430 ft; within 50 miles, large variations in elevation — a maximum elevation change of 2,454 ft.

The land around Portsmouth is covered by trees (45%), water (22%) and artificial surfaces (21%) within 2 miles, trees (49%) and water (36%) within 10 miles, and trees (61%) and water (32%) within 50 miles.

2 miles
161 ft
10 miles
430 ft
50 miles
2,454 ft
treesgrasslandartificial surfaceswaterwetland
August weather nearby: Dover 9.9 mi · Amesbury 17 mi · Rochester 19 mi · Newburyport 19 mi · Sanford 25 mi · Haverhill 26 mi · Salem 30 mi · Derry Village 31 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 Portsmouth (43.077°, -70.7577°, elevation 20 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). Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).