San Borja weather in September

In September, San Borja sees average daytime highs of 33°C and overnight lows near 21°C, with 118 mm of rain across 10.8 wet days and about 11.9 hours of daylight. It is the 1st-warmest and 8th-wettest month of the year here.

Day-to-day highs hold fairly steady near 33°C through the month. The sky is clear or mostly clear about 34% of the time in September, and the air most often feels oppressive.

Daylight stretches from about 11 h 42 min at the start of September to 12 h 06 min by month's end. Set against the rest of the year, September is San Borja's 4th-clearest and 1st-windiest month. For the whole year in context, see San Borja's year-round climate.

Daytime high
33°
1st warmest
Overnight low
21°
5th coldest
Rainfall
118 mm
10.8 wet days
Daylight
11 h 54 min
6:24 AM – 6:19 PM
Cloud cover
56%
4th clearest
Wind
8 km/h
1st windiest
Solar energy
5.39 kWh/m²
Travel score
3.6
out of 10

San Borja is Municipio en Bolivia.

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 33°C through the month.

A typical September day in San Borja reaches about 33°C in the afternoon and slips back to 21°C overnight — a 12°C spread between the day's warmth and the night's chill. On most days the high lands between 26°C and 38°C. Set against its neighbours, September runs about 2°C warmer than August and on par with October.

15°20°25°30°35°40°151015202530
Avg high (°C)Avg low (°C)
13220
23220
33220
43221
53221
63221
73221
83221
93221
103321
113321
123321
133321
143321
153321
163321
173321
183321
193321
203321
213321
223322
233322
243322
253322
263322
273322
283322
293322
303322

How September really feels in San Borja

Once humidity and wind are folded in, September averages 30 days that feel above 32°C and 0 that feel at or below 0°C — the comfort signal a plain temperature reading hides.

Days feeling ≥ 32°C
30
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

The story in September is heat — humidity pushes the afternoon "feels like" well above the raw temperature.

San Borja weather by month

How September compares with the rest of the year at a glance. September is the 1st-warmest and 8th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan31° / 23°34827.112.82.7
Feb31° / 23°30323.312.52.9
Mar31° / 23°2652412.13.0
Apr30° / 22°15416.711.73.9
May29° / 20°8611.311.35.5
Jun28° / 19°577.611.16.5
Jul28° / 18°496.211.26.5
Aug31° / 19°60711.54.9
Sep33° / 21°11810.811.93.6
Oct33° / 23°17817.612.33.0
Nov32° / 23°21219.412.73.0
Dec31° / 23°29424.612.92.8

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 34% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 20% of September, with mostly cloudy or overcast conditions the remaining 46%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16535
26535
36436
46337
56238
66139
76040
85941
95941
105842
115743
125644
135545
145446
155347
165347
175347
185248
195149
205149
215050
224951
235050
244951
254951
264852
274852
284753
294753
304654

Chance of precipitation in September

Any precipitation

San Borja gets around 118 mm of rain over 10.8 wet days in September. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 36% and peaks near 46% on the wettest days. The odds climb toward the end of the month.

0%20%40%60%151015202530
Rain chance (%)
128
229
329
430
531
631
732
832
933
1033
1133
1234
1334
1435
1535
1636
1736
1837
1937
2038
2138
2239
2340
2440
2541
2642
2743
2844
2945
3046

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the oppressive band about 45% of days. Sticky, muggy-or-worse air turns up on roughly 76% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)Miserable (%)
18101534320
28101534330
38101434340
47101434350
57101434360
6791434360
7691433370
8691433380
9681433390
10581333401
11581333411
12571332421
13471332431
14471232441
15471231451
16471231461
17471230471
18471130471
19471129481
20371129492
21361128502
22361128502
23361127512
24361126522
25351026542
26351025552
27251024572
28241023592
29241023592
30241022602

Wind in September

Winds average 8 km/h in September, the windiest month of the year.

Across September, daily wind ranges from about 8 km/h on the calmest days to 8 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (km/h)Feels
18calm
28calm
38calm
48calm
58calm
68calm
78calm
88calm
98calm
108calm
118calm
128calm
138calm
148calm
158calm
168calm
178calm
188calm
198calm
208calm
218calm
228calm
238calm
248calm
258calm
268calm
278calm
288calm
298calm
308calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 11 h 42 min at the start of September to 12 h 06 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 24 minutes over September. Sunrise moves from 6:35 AM to 6:13 AM, and sunset from 6:18 PM to 6:20 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
111.76:356:18
211.76:356:18
311.76:346:18
411.76:336:18
511.86:326:18
611.86:326:18
711.86:316:18
811.86:306:18
911.86:296:18
1011.86:296:19
1111.86:286:19
1211.96:276:19
1311.96:266:19
1411.96:256:19
1511.96:256:19
1611.96:246:19
1711.96:236:19
1811.96:226:19
1912.06:216:19
2012.06:216:19
2112.06:206:19
2212.06:196:19
2312.06:186:19
2412.06:176:19
2512.06:176:19
2612.16:166:19
2712.16:156:20
2812.16:146:20
2912.16:146:20
3012.16:136:20

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.39 kWh/m².

For context, solar energy here swings from a low near 3.68 kWh/m² to a high of 5.46 kWh/m² in October across the year — September's 5.39 kWh/m² sits near the top of that range.

0246151015202530
Solar energy (kWh/m²)Level
15.2Bright
25.2Bright
35.2Bright
45.2Bright
55.2Bright
65.2Bright
75.3Bright
85.3Bright
95.3Bright
105.3Bright
115.3Bright
125.3Bright
135.3Bright
145.4Bright
155.4Bright
165.4Bright
175.4Bright
185.4Bright
195.5Bright
205.5Bright
215.5Bright
225.5Bright
235.5Bright
245.5Bright
255.5Bright
265.5Bright
275.5Bright
285.5Bright
295.5Bright
305.5Bright
Planning a trip in September

Hazard calendar for San Borja

In seasonPeak

None of San Borja's seasonal hazards are active in September. The full-year calendar below shows when the rainy season, cyclone risk and dust haze do peak.

San Borja's rainy season runs October–March, when most of the year's rain falls.

Rainy season
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is September a good time to visit San Borja?

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

3.6
Sightseeing
6th-best month of the year
6.2
Beach & pool
5th-best month of the year

September is a weaker month for outdoor sightseeing in San Borja. The water and warmth also suit a beach or pool day.

What to pack for San Borja in September

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

In September, San Borja sees daytime highs around 33°C and nights near 21°C. Pack light clothes. Worth having: rain gear and sun protection. About 11 days see rain.

light clothesrain gearsun protection

UV index in San Borja in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 8 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in San Borja peaks around January 21 at about 15 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near September 11 at about 8 (very high).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecExtremeVery highExtremeJan 21UV 15Sep 11UV 8
UV index (midday)Level
Jan16Extreme
Feb15Extreme
Mar14Extreme
Apr11Extreme
May9Very high
Jun8Very high
Jul8Very high
Aug8Very high
Sep8Very high
Oct12Extreme
Nov14Extreme
Dec13Extreme

Air quality in San Borja 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 San Borja is worst in September — around 50 µg/m³ PM2.5 (poor), about 6.4× the cleanest month (May, 8 µg/m³).

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

0204060JanFebMarAprMayJunJulAugSepOctNovDecGoodModeratePoorModerateSep 2350 µg/m³May 218 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb12Good
Mar11Good
Apr9Good
May8Good
Jun8Good
Jul11Good
Aug22Moderate
Sep50Poor
Oct50Poor
Nov27Moderate
Dec11Good
Location & terrain

Where is San Borja?

San Borja sits at 14.9°S, 66.7°W, 195 m above sea level, in Bolivia. The nearest listed city is Caranavi, 140 km away.

CaranaviTrinidadSorataLa PazQuimeAchocallaLajaViacha

Topography around San Borja

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of San Borja.

Within 3 km, the terrain around San Borja has only modest variations in elevation — a maximum elevation change of 21 m around an average of 194 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 44 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,527 m.

The land around San Borja is covered by grassland (61%) and trees (28%) within 3 km, grassland (63%) and trees (30%) within 16 km, and trees (75%) and grassland (23%) within 80 km.

3 km
21 m
16 km
44 m
80 km
1,527 m
treesshrubsgrasslandartificial surfaceswaterwetland
September weather nearby: Caranavi 140 km · Trinidad 198 km · Sorata 228 km · La Paz 237 km · Quime 242 km · Achocalla 243 km · Laja 256 km · Viacha 260 km

Bolivia travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type A / B / C
230 V · 50 Hz
Prices
≈ 40% of US
price level, 2025
GDP per capita
$5,148
2025
Happiness
5.8 / 10
World Happiness, 2025
Homicide rate
4.4
per 100k, 2023
Road deaths
21.1
per 100k/yr, 2019
Income group
Lower middle
World Bank
English
Moderate
EF EPI 521
Religion
Roman Catholic 65%Protestant 20%none 6%other 5%

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 San Borja (-14.852°, -66.7495°, elevation 195 m), 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).