Altsasu weather in December

In December, Altsasu sees average daytime highs of 9°C and overnight lows near 3°C, with 101 mm of precipitation across 13.8 wet days and about 8.9 hours of daylight. It is the 11th-warmest and 6th-wettest month of the year here.

Day-to-day highs hold fairly steady near 9°C through the month. The sky is clear or mostly clear about 16% of the time in December, and the air most often feels dry.

Daylight stretches from about 9 h 06 min at the start of December to 8 h 54 min by month's end. Set against the rest of the year, December is Altsasu's 11th-clearest and 3rd-windiest month. For the whole year in context, see Altsasu's year-round climate.

Daytime high
11th warmest
Overnight low
3rd coldest
Precipitation
101 mm
13.8 wet days
Daylight
8 h 54 min
8:39 AM – 5:30 PM
Cloud cover
72%
11th clearest
Wind
10 km/h
3rd windiest
Solar energy
1.42 kWh/m²
Travel score
1.8
out of 10

Altsasu is municipality of Spain.

Density
276/km²
people per km²

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

Temperature in December

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 9°C through the month.

A typical December day in Altsasu reaches about 9°C in the afternoon and slips back to 3°C overnight — a 6°C spread between the day's warmth and the night's chill. On most days the high lands between 5°C and 13°C. Set against its neighbours, December runs about 3°C cooler than November and on par with January.

-5°10°15°151015202531
Avg high (°C)Avg low (°C)
1104
2104
3104
4104
5104
6104
7104
8104
9104
10104
11104
1293
1393
1493
1593
1693
1793
1893
1993
2093
2193
2293
2393
2493
2593
2693
2793
2893
2993
3093
3193

How December really feels in Altsasu

Once humidity and wind are folded in, December averages 0 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
0
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

December sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Altsasu weather by month

How December compares with the rest of the year at a glance. December is the 11th-warmest and 6th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / 11315.13.39.21.5
Feb10° / 10313.6410.22.0
Mar13° / 100142.211.63.2
Apr15° / 113160.613.13.7
May18° / 10615.3014.45.0
Jun21° / 12°7911.6015.16.2
Jul23° / 14°5910.4014.86.9
Aug24° / 14°6511.8013.86.8
Sep21° / 12°7011.6012.36.2
Oct18° / 9612.70.110.85.3
Nov12° / 127150.89.52.8
Dec / 10113.82.28.91.8

Cloud cover in December

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 16% of the time in December.

Beyond those clear spells, partly cloudy skies cover about 13% of December, with mostly cloudy or overcast conditions the remaining 71%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
12872
22872
32872
42872
52872
62872
72971
82971
92971
103070
113070
123070
133070
143070
153070
163070
172971
182971
193070
202872
212872
222872
232872
242773
252773
262773
272872
282872
292872
302971
312971

Chance of precipitation in December

Any precipitationSnow

Altsasu gets around 101 mm of rain and snow over 13.8 wet days in December. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable precipitation averages around 45% and peaks near 51% on the wettest days, and about 2 days bring snow.

0%20%40%60%151015202531
Rain chance (%)Snow chance (%)
1516
2516
3506
4506
5496
6486
7476
8476
9466
10456
11446
12446
13436
14426
15426
16416
17417
18417
19417
20427
21427
22427
23427
24437
25437
26437
27447
28447
29447
30457
31457

Humidity in December

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, December lands in the dry band about 100% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)
1100
2100
3100
4100
5100
6100
7100
8100
9100
10100
11100
12100
13100
14100
15100
16100
17100
18100
19100
20100
21100
22100
23100
24100
25100
26100
27100
28100
29100
30100
31100

Wind in December

Winds average 10 km/h in December.

Across December, daily wind ranges from about 10 km/h on the calmest days to 10 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202531
Wind speed (km/h)Feels
110calm
210calm
310calm
410calm
510calm
610calm
710calm
810calm
910calm
1010calm
1110calm
1210calm
1310calm
1410calm
1510calm
1610calm
1710calm
1810calm
1910calm
2010calm
2110calm
2210calm
2310calm
2410calm
2510calm
2610calm
2710calm
2810calm
2910calm
3010calm
3110calm

Sunrise & sunset in December

DaylightNight

Daylight runs from about 9 h 06 min at the start of December to 8 h 54 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 12 minutes over December. Sunrise moves from 8:26 AM to 8:46 AM, and sunset from 5:31 PM to 5:38 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
19.18:265:31
29.08:275:30
39.08:285:30
49.08:295:30
59.08:305:30
69.08:315:30
79.08:325:29
88.98:335:29
98.98:345:29
108.98:355:29
118.98:365:30
128.98:365:30
138.98:375:30
148.98:385:30
158.98:395:30
168.98:395:30
178.88:405:31
188.88:415:31
198.88:415:31
208.88:425:32
218.88:425:32
228.88:435:33
238.88:435:33
248.88:445:34
258.88:445:34
268.88:445:35
278.88:455:35
288.98:455:36
298.98:455:37
308.98:455:37
318.98:465:38

Solar energy in December

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in December, about 1.42 kWh/m² — the year's lowest.

For context, solar energy here swings from a low near 1.42 kWh/m² to a high of 5.91 kWh/m² in June across the year — December's 1.42 kWh/m² sits near the bottom.

00.511.52151015202531
Solar energy (kWh/m²)Level
11.5Dim
21.5Dim
31.5Dim
41.5Dim
51.4Dim
61.4Dim
71.4Dim
81.4Dim
91.4Dim
101.4Dim
111.4Dim
121.4Dim
131.4Dim
141.4Dim
151.4Dim
161.4Dim
171.4Dim
181.4Dim
191.4Dim
201.4Dim
211.4Dim
221.4Dim
231.4Dim
241.4Dim
251.4Dim
261.4Dim
271.4Dim
281.4Dim
291.4Dim
301.4Dim
311.5Dim
Planning a trip in December

Is December a good time to visit Altsasu?

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

1.8
Sightseeing
11th-best month of the year
0.0
Beach & pool
9th-best month of the year

December is a weaker month for outdoor sightseeing in Altsasu.

What to pack for Altsasu in December

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

In December, Altsasu sees daytime highs around 9°C and nights near 3°C. Pack a warm layer. Worth having: rain gear. About 14 days see rain.

a warm layerrain gear

Sea temperature near Altsasu in December

The nearest coast averages about 14°C in December — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 53 km away) is warmest in August at about 22°C and coldest in February near 12°C.

It's comfortable for a long swim from Jul 2 to Sep 25 — about 2.8 months when the water holds above 20°C.

10°15°20°25°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmcomfortable to swim
Sea temperature (°C)Comfort
Jan13Bracing
Feb12Bracing
Mar13Bracing
Apr14Bracing
May16Cool
Jun19Cool
Jul21Refreshing
Aug22Refreshing
Sep21Refreshing
Oct18Cool
Nov16Cool
Dec14Bracing

UV index in Altsasu in December

LowModerateHighVery highExtreme

Clear-sky midday UV in December peaks around 1. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Altsasu peaks around July 15 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 20 at about 1 (low).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighModerateLowJul 15UV 9Dec 20UV 1
UV index (midday)Level
Jan2Low
Feb2Moderate
Mar5Moderate
Apr6High
May7High
Jun9Very high
Jul9Very high
Aug8Very high
Sep6High
Oct4Moderate
Nov2Low
Dec1Low
Location & terrain

Where is Altsasu?

Altsasu sits at 42.9°N, 2.2°W, 0 m above sea level, in Spain. The nearest listed city is Tolosa, 27 km away.

Topography around Altsasu

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

Within 3 km, the terrain around Altsasu has large variations in elevation — a maximum elevation change of 625 m around an average of 594 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 1,365 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,532 m.

The land around Altsasu is covered by trees (66%) and grassland (24%) within 3 km, trees (72%) and grassland (23%) within 16 km, and trees (44%) and cropland (22%) within 80 km.

3 km
625 m
16 km
1,365 m
80 km
1,532 m
treesshrubsgrasslandcroplandartificial surfaceswater
December weather nearby: Tolosa 27 km · Arrasate / Mondragón 32 km · Eibar 40 km · Barañáin 41 km · Oria 41 km · Gasteiz / Vitoria 42 km · Ermitagaña 42 km · Ermua 42 km

Spain travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type C / F
230 V · 50 Hz
Prices
≈ 65% of US
price level, 2025
GDP per capita
$38,627
2025
Happiness
6.5 / 10
World Happiness, 2025
Safe drinking water
99%
of population, 2024
Homicide rate
0.7
per 100k, 2023
Road deaths
3.9
per 100k/yr, 2019
Income group
High
World Bank
English
Moderate
EF EPI 540
Religion
Roman Catholic 58%atheist 16%agnostic 11%non-believer 11%

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 Altsasu (42.9°, -2.1652°, elevation 0 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. 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).