Hilo weather in September

In September, Hilo sees average daytime highs of 77°F and overnight lows near 72°F, with 4.5 in of rain across 22 wet days and about 12.1 hours of daylight. It is the 1st-warmest and 12th-wettest month of the year here.

Day-to-day highs hold fairly steady near 77°F through the month. The sky is clear or mostly clear about 37% of the time in September, and the air most often feels muggy.

Daylight stretches from about 12 h 24 min at the start of September to 11 h 48 min by month's end. Set against the rest of the year, September is Hilo's 2nd-clearest and 12th-windiest month. For the whole year in context, see Hilo's year-round climate.

Daytime high
77°
1st warmest
Overnight low
72°
12th coldest
Rainfall
4.5 in
22 wet days
Daylight
12 h 06 min
6:11 AM – 6:18 PM
Cloud cover
50%
2nd clearest
Wind
5 mph
12th windiest
Solar energy
6.01 kWh/m²
Travel score
5.1
out of 10

Hilo is human settlement and census-designated place in Hawaii, United States.

Density
287/km²
people per km²

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 77°F through the month.

A typical September day in Hilo reaches about 77°F in the afternoon and slips back to 72°F overnight — a 5°F spread between the day's warmth and the night's chill. On most days the high lands between 75°F and 79°F. Set against its neighbours, September runs on par with August and on par with October.

65°70°75°80°85°151015202530
Avg high (°F)Avg low (°F)
17772
27772
37772
47772
57772
67772
77772
87772
97772
107772
117772
127772
137772
147772
157772
167772
177772
187772
197772
207772
217772
227772
237772
247772
257772
267772
277772
287772
297772
307772

Hilo weather by month

How September compares with the rest of the year at a glance. September is the 1st-warmest and 12th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysDaylight (hours)Travel score
Jan73° / 67°5.816.810.96.0
Feb72° / 67°6.617.211.35.5
Mar72° / 67°9.123.511.94.7
Apr73° / 68°7.124.812.44.5
May74° / 69°5.723.712.94.9
Jun75° / 70°4.724.113.24.8
Jul76° / 71°5.725.813.14.6
Aug77° / 72°6.725.612.74.6
Sep77° / 72°4.52212.15.1
Oct77° / 71°5.42311.55.0
Nov75° / 70°7.523.211.14.8
Dec73° / 68°7.922.210.85.1

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 37% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 32% of September, with mostly cloudy or overcast conditions the remaining 31%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
17030
27030
37030
47030
57030
67030
77030
87030
97030
107030
117030
127129
137030
147030
157030
167129
177129
187030
197030
207129
217030
227030
236931
246832
256832
266634
276634
286535
296436
306337

Chance of precipitation in September

Any precipitation

Hilo gets around 4.5 in of rain over 22 wet days in September, the driest month. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 74% and peaks near 76% on the wettest days.

0%20%40%60%80%151015202530
Rain chance (%)
174
274
373
473
573
673
773
874
974
1074
1175
1275
1375
1476
1576
1676
1776
1875
1975
2075
2174
2274
2373
2472
2572
2671
2771
2870
2970
3070

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the muggy band about 73% of days. Sticky, muggy-or-worse air turns up on roughly 95% of them.

0%25%50%75%100%151015202530
Humid (%)Muggy (%)Oppressive (%)
157421
257421
357421
457421
557421
657322
757322
857322
967222
1067222
1167222
1267321
1367321
1467321
1567321
1667321
1767321
1867321
1967321
2067321
2167321
2267321
2367321
2467321
2557421
2657421
2757421
2857421
2957421
3057520

Wind in September

Winds average 5 mph in September, the calmest month.

Across September, daily wind ranges from about 5 mph on the calmest days to 6 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
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
286calm
296calm
306calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 24 min at the start of September to 11 h 48 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 36 minutes over September. Sunrise moves from 6:08 AM to 6:14 AM, and sunset from 6:32 PM to 6:05 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.46:086:32
212.46:086:31
312.46:096:30
412.36:096:29
512.36:096:28
612.36:096:27
712.36:106:26
812.36:106:26
912.26:106:25
1012.26:106:24
1112.26:106:23
1212.26:116:22
1312.26:116:21
1412.16:116:20
1512.16:116:19
1612.16:116:18
1712.16:126:17
1812.16:126:16
1912.16:126:15
2012.06:126:14
2112.06:126:13
2212.06:136:12
2312.06:136:11
2412.06:136:10
2511.96:136:10
2611.96:136:09
2711.96:146:08
2811.96:146:07
2911.96:146:06
3011.86:146:05

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 6.01 kWh/m².

For context, solar energy here swings from a low near 4.17 kWh/m² to a high of 6.68 kWh/m² in June across the year — September's 6.01 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
16.3Intense
26.3Intense
36.2Intense
46.2Intense
56.2Intense
66.2Intense
76.2Intense
86.2Intense
96.1Intense
106.1Intense
116.1Intense
126.1Intense
136.0Intense
146.0Intense
156.0Intense
166.0Bright
176.0Bright
185.9Bright
195.9Bright
205.9Bright
215.9Bright
225.9Bright
235.8Bright
245.8Bright
255.8Bright
265.8Bright
275.8Bright
285.7Bright
295.7Bright
305.7Bright
Planning a trip in September

Hazard calendar for Hilo

In seasonPeak

In September, Hilo sits inside its pacific hurricane season. The full year is below, with each hazard's peak months called out.

Hilo sits in the eastern Pacific hurricane zone; the season peaks August–September.

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

Is September a good time to visit Hilo?

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

5.1
Sightseeing
3rd-best month of the year
4.6
Beach & pool
1st-best month of the year

September is a reasonable time to visit Hilo for sightseeing.

What to pack for Hilo in September

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

In September, Hilo sees daytime highs around 77°F and nights near 72°F. Pack rain gear and sun protection. Worth having: light clothes. About 22 days see rain.

rain gearsun protectionlight clothes

Sea temperature near Hilo in September

The nearest coast averages about 80°F in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 11 mi away) is warmest in September at about 80°F and coldest in March near 75°F.

The water stays above 68°F all year — warm enough for a swim any month.

74°76°78°80°82°JanFebMarAprMayJunJulAugSepOctNovDecrefreshingwarmcomfortable to swim
Sea temperature (°F)Comfort
Jan76Warm
Feb75Warm
Mar75Warm
Apr76Warm
May77Warm
Jun78Warm
Jul79Warm
Aug79Warm
Sep80Warm
Oct80Warm
Nov78Warm
Dec77Warm

UV index in Hilo in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 13 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Hilo peaks around August 15 at about 14 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 16 at about 7 (high).

The index reaches 3 or more — the level where the WHO recommends sun protection — every month of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecVery highExtremeVery highHighAug 15UV 14Dec 16UV 7
UV index (midday)Level
Jan8Very high
Feb10Very high
Mar12Extreme
Apr14Extreme
May11Extreme
Jun13Extreme
Jul13Extreme
Aug14Extreme
Sep13Extreme
Oct10Extreme
Nov8Very high
Dec7High

Air quality in Hilo in September

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where September falls, not just the annual average.

Air quality in Hilo is worst in January — around 28 µg/m³ PM2.5 (moderate), about 1.7× the cleanest month (July, 16 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateJan 2128 µg/m³Jul 1917 µg/m³
PM2.5 (µg/m³)Level
Jan28Moderate
Feb27Moderate
Mar26Moderate
Apr23Moderate
May22Moderate
Jun19Moderate
Jul16Moderate
Aug18Moderate
Sep21Moderate
Oct25Moderate
Nov22Moderate
Dec24Moderate
Location & terrain

Where is Hilo?

Hilo sits at 19.7°N, 155.1°W, 59 ft above sea level, in United States. The nearest listed city is Kīhei, 113 mi away.

Topography around Hilo

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

Within 2 miles, the terrain around Hilo has only modest variations in elevation — a maximum elevation change of 774 ft around an average of 197 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 3,606 ft; within 50 miles, extreme variations in elevation — a maximum elevation change of 13,750 ft.

The land around Hilo is covered by trees (34%), water (29%) and grassland (22%) within 2 miles, trees (42%) and water (29%) within 10 miles, and water (49%) and grassland (20%) within 50 miles.

2 miles
774 ft
10 miles
3,606 ft
50 miles
13,750 ft
treesshrubsgrasslandartificial surfacesbare terrainwater
September weather nearby: Kīhei 113 mi · Kahului 120 mi · Wailuku 122 mi · Lahaina 130 mi · Hawai‘i Kai 201 mi · East Honolulu 201 mi · Niu Valley 202 mi · Kuliouou - Kalani Iki 203 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 Hilo (19.7299°, -155.0907°, elevation 59 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. 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).