União weather in December

In December, União sees average daytime highs of 35°C and overnight lows near 25°C, with 84 mm of rain across 9.7 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 6th-wettest month of the year here.

Highs ease over the month, from about 36°C in the first days to 34°C by the end. The sky is clear or mostly clear about 24% of the time in December, and the air most often feels oppressive.

Daylight stretches from about 12 h 12 min at the start of December to 12 h 18 min by month's end. Set against the rest of the year, December is União's 8th-clearest and 6th-windiest month. For the whole year in context, see União's year-round climate.

Daytime high
35°
4th warmest
Overnight low
25°
10th coldest
Rainfall
84 mm
9.7 wet days
Daylight
12 h 18 min
5:40 AM – 5:56 PM
Cloud cover
63%
8th clearest
Wind
7 km/h
6th windiest
Solar energy
5.77 kWh/m²
Travel score
2.4
out of 10

União is settlement in Uniao, Piaui, Brazil.

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

Temperature in December

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 36°C in the first days to 34°C by the end.

A typical December day in União reaches about 35°C in the afternoon and slips back to 25°C overnight — a 10°C spread between the day's warmth and the night's chill. On most days the high lands between 32°C and 38°C. Set against its neighbours, December runs about 1°C cooler than November and about 3°C warmer than January.

20°25°30°35°40°151015202531
Avg high (°C)Avg low (°C)
13625
23625
33625
43625
53625
63625
73625
83625
93625
103625
113625
123525
133525
143525
153525
163525
173525
183525
193525
203525
213525
223525
233525
243525
253425
263425
273425
283424
293424
303424
313424

How December really feels in União

Once humidity and wind are folded in, December averages 31 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
31
16 feel dangerously hot (≥ 39°C)
Days feeling ≤ C
0
wind chill below the day's low

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

União weather by month

How December compares with the rest of the year at a glance. December is the 4th-warmest and 6th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan33° / 24°22821.812.22.6
Feb32° / 23°29622.212.22.7
Mar31° / 23°36327122.6
Apr31° / 23°32524.611.92.8
May32° / 23°14315.111.83.6
Jun33° / 23°234.611.74.2
Jul34° / 23°121.711.84.0
Aug35° / 24°20.511.93.2
Sep36° / 24°30.6122.3
Oct37° / 25°101.512.11.8
Nov36° / 25°354.512.22.0
Dec35° / 25°849.712.32.4

Cloud cover in December

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 24% of the time in December.

Beyond those clear spells, partly cloudy skies cover about 20% of December, with mostly cloudy or overcast conditions the remaining 56%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
15347
25248
35248
45248
55248
65149
75149
85050
94852
104852
114753
124753
134555
144456
154555
164456
174258
184159
194159
204060
214060
224060
233961
243961
253862
263862
273763
283763
293664
303664
313664

Chance of precipitation in December

Any precipitation

União gets around 84 mm of rain over 9.7 wet days in December. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 33% and peaks near 54% on the wettest days. The odds climb toward the end of the month.

0%20%40%60%151015202531
Rain chance (%)
119
219
319
420
520
621
721
822
923
1024
1125
1226
1327
1428
1530
1631
1732
1834
1935
2036
2137
2239
2340
2442
2543
2645
2747
2848
2950
3052
3154

Humidity in December

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, December lands in the oppressive band about 55% of days. Sticky, muggy-or-worse air turns up on roughly 97% of them.

0%25%50%75%100%151015202531
Humid (%)Muggy (%)Oppressive (%)Miserable (%)
1749422
2749422
3749422
4750422
5650422
6649432
7649432
8548442
9548452
10547462
11446472
12446492
13345502
14344512
15343513
16241543
17240553
18239563
19237583
20236584
21234604
22233614
23231625
24230635
25128656
26126676
27224677
28222697
29220708
30219718
31217729

Wind in December

Winds average 7 km/h in December.

Across December, daily wind ranges from about 7 km/h on the calmest days to 8 km/h at its breeziest. It stays fairly steady from day to day.

0246810151015202531
Wind speed (km/h)Feels
18calm
28calm
38calm
48calm
58calm
68calm
78calm
88calm
98calm
108calm
118calm
128calm
138calm
148calm
157calm
167calm
177calm
187calm
197calm
207calm
217calm
227calm
237calm
247calm
257calm
267calm
277calm
287calm
297calm
307calm
317calm

Sunrise & sunset in December

DaylightNight

Daylight runs from about 12 h 12 min at the start of December to 12 h 18 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 6 minutes over December. Sunrise moves from 5:34 AM to 5:47 AM, and sunset from 5:49 PM to 6:02 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
112.25:345:49
212.25:345:49
312.35:345:49
412.35:355:50
512.35:355:50
612.35:365:51
712.35:365:51
812.35:365:52
912.35:375:52
1012.35:375:53
1112.35:385:53
1212.35:385:54
1312.35:385:54
1412.35:395:55
1512.35:395:55
1612.35:405:56
1712.35:405:56
1812.35:415:56
1912.35:415:57
2012.35:425:57
2112.35:425:58
2212.35:425:58
2312.35:435:59
2412.35:435:59
2512.35:446:00
2612.35:446:00
2712.35:456:01
2812.35:456:01
2912.35:466:02
3012.35:466:02
3112.35:476:02

Solar energy in December

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in December, about 5.77 kWh/m².

For context, solar energy here swings from a low near 4.76 kWh/m² to a high of 6.71 kWh/m² in October across the year — December's 5.77 kWh/m² falls in the middle.

0246151015202531
Solar energy (kWh/m²)Level
16.1Intense
26.0Intense
36.0Intense
46.0Intense
56.0Intense
66.0Bright
76.0Bright
86.0Bright
95.9Bright
105.9Bright
115.9Bright
125.8Bright
135.8Bright
145.8Bright
155.8Bright
165.7Bright
175.7Bright
185.7Bright
195.7Bright
205.6Bright
215.6Bright
225.6Bright
235.6Bright
245.6Bright
255.5Bright
265.5Bright
275.5Bright
285.5Bright
295.5Bright
305.4Bright
315.4Bright
Planning a trip in December

Hazard calendar for União

In seasonPeak

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

União's monsoon runs January–April, when most of the year's rain falls.

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

Is December a good time to visit União?

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

2.4
Sightseeing
9th-best month of the year
5.2
Beach & pool
6th-best month of the year

December is a weaker month for outdoor sightseeing in União.

What to pack for União in December

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

In December, União sees daytime highs around 35°C and nights near 25°C. Pack light clothes. Worth having: rain gear and sun protection. About 10 days see rain.

light clothesrain gearsun protection

UV index in União in December

LowModerateHighVery highExtreme

Clear-sky midday UV in December peaks around 11 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in União peaks around March 14 at about 15 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near July 24 at about 10 (very high).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecExtremeVery highExtremeMar 14UV 15Jul 24UV 10
UV index (midday)Level
Jan13Extreme
Feb14Extreme
Mar15Extreme
Apr13Extreme
May11Extreme
Jun10Very high
Jul10Very high
Aug10Very high
Sep12Extreme
Oct12Extreme
Nov11Extreme
Dec11Extreme

Air quality in União in December

GoodModeratePoorUnhealthyVery unhealthy

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

Air quality in União is worst in November — around 22 µg/m³ PM2.5 (moderate), about 2.1× the cleanest month (June, 10 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodModerateNov 922 µg/m³Jun 1211 µg/m³
PM2.5 (µg/m³)Level
Jan15Moderate
Feb16Moderate
Mar14Moderate
Apr13Moderate
May12Good
Jun10Good
Jul14Moderate
Aug20Moderate
Sep17Moderate
Oct22Moderate
Nov22Moderate
Dec18Moderate
Location & terrain

Where is União?

União sits at 4.6°S, 42.9°W, 60 m above sea level, in Brazil. The nearest listed city is José de Freitas, 37 km away.

Topography around União

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

Within 3 km, the terrain around União has only modest variations in elevation — a maximum elevation change of 96 m around an average of 54 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 139 m; within 80 km, significant variations in elevation — a maximum elevation change of 318 m.

The land around União is covered by grassland (40%) and trees (24%) within 3 km, trees (58%) and grassland (23%) within 16 km, and trees (66%) within 80 km.

3 km
96 m
16 km
139 m
80 km
318 m
treesshrubsgrasslandcroplandartificial surfacesbare terrainwater
December weather nearby: José de Freitas 37 km · Coelho Neto 40 km · Miguel Alves 47 km · Teresina 56 km · Timon 57 km · Caxias 62 km · Altos 67 km · Aldeias Altas 67 km

Brazil travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type C / N
127 / 220 V · 60 Hz
Prices
≈ 46% of US
price level, 2025
GDP per capita
$10,713
2025
Happiness
6.6 / 10
World Happiness, 2025
Safe drinking water
89%
of population, 2024
Homicide rate
19.3
per 100k, 2023
Road deaths
16
per 100k/yr, 2019
Income group
Upper middle
World Bank
English
Low
EF EPI 482
Religion
Roman Catholic 57%Evangelical 27%none 9%other 4%

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 União (-4.5858°, -42.8642°, elevation 60 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).