Sunnyside weather in December

In December, Sunnyside sees average daytime highs of 39°F and overnight lows near 28°F, with 1.7 in of precipitation across 9 wet days and about 8.5 hours of daylight. It is the 12th-warmest and 1st-wettest month of the year here.

Highs ease over the month, from about 41°F in the first days to 38°F by the end. The sky is clear or mostly clear about 22% of the time in December, and the air most often feels dry.

Daylight stretches from about 8 h 42 min at the start of December to 8 h 30 min by month's end. Set against the rest of the year, December is Sunnyside's 11th-clearest and 11th-windiest month. For the whole year in context, see Sunnyside's year-round climate.

Daytime high
39°
12th warmest
Overnight low
28°
2nd coldest
Precipitation
1.7 in
9 wet days
Daylight
8 h 24 min
7:44 AM – 4:09 PM
Cloud cover
67%
11th clearest
Wind
5 mph
11th windiest
Solar energy
1.3 kWh/m²
Travel score
0.0
out of 10

Sunnyside is city in Yakima County, Washington, United States.

Density
950/km²
people per km²
Founded
1902

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 41°F in the first days to 38°F by the end.

A typical December day in Sunnyside reaches about 39°F in the afternoon and slips back to 28°F overnight — a 12°F spread between the day's warmth and the night's chill. On most days the high lands between 28°F and 50°F. Set against its neighbours, December runs about 9°F cooler than November and on par with January.

20°30°40°50°60°151015202531
Avg high (°F)Avg low (°F)
14229
24229
34129
44129
54128
64028
74028
84028
94028
104028
114028
124028
134028
143928
153928
163928
173928
183928
193927
203927
213927
223827
233827
243827
253827
263827
273827
283827
293827
303827
313827

How December really feels in Sunnyside

Once humidity and wind are folded in, December averages 0 days that feel above 90°F and 31 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
31
wind chill below the day's low

The story in December is cold — wind chill drags the overnight "feels like" below the raw low.

Sunnyside weather by month

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

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan40° / 28°1.59.23.58.80.1
Feb47° / 31°1.16.31.9101.5
Mar55° / 36°1.06.60.611.63.9
Apr65° / 43°0.74.60.113.36.5
May75° / 51°0.74.2014.77.7
Jun82° / 57°0.43015.57.2
Jul91° / 63°0.21.3015.24.6
Aug90° / 61°0.21.10145.1
Sep80° / 53°0.31.9012.38.0
Oct64° / 43°1.05.10.110.76.4
Nov48° / 34°1.37.819.22.0
Dec39° / 28°1.793.58.50.0

Cloud cover in December

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 22% of the time in December.

Beyond those clear spells, partly cloudy skies cover about 12% of December, with mostly cloudy or overcast conditions the remaining 65%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
13961
24060
34060
43961
53862
63862
73763
83763
93664
103565
113466
123466
133367
143367
153367
163268
173268
183367
193268
203268
213268
223367
233268
243268
253367
263367
273367
283367
293466
303565
313466

Chance of precipitation in December

Any precipitationSnow

Sunnyside gets around 1.7 in of rain and snow over 9 wet days in December, the wettest month. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable precipitation averages around 29% and peaks near 31% on the wettest days, and about 4 days bring snow.

0%10%20%30%40%151015202531
Rain chance (%)Snow chance (%)
1288
2288
3288
4288
5298
6298
7299
8289
9289
10289
112910
122910
132910
142911
152911
163011
173012
183012
192912
202913
213013
223013
233014
243014
253014
263014
273014
283014
293014
303114
313114

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 5 mph in December.

Across December, daily wind ranges from about 4 mph on the calmest days to 5 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202531
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
224calm
234calm
244calm
254calm
264calm
274calm
284calm
294calm
304calm
315calm

Sunrise & sunset in December

DaylightNight

Daylight runs from about 8 h 42 min at the start of December to 8 h 30 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 7:30 AM to 7:50 AM, and sunset from 4:10 PM to 4:17 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
18.77:304:10
28.77:314:10
38.67:324:09
48.67:334:09
58.67:344:09
68.67:354:09
78.57:364:08
88.57:374:08
98.57:384:08
108.57:394:08
118.57:404:08
128.57:404:08
138.57:414:08
148.47:424:08
158.47:434:09
168.47:444:09
178.47:444:09
188.47:454:09
198.47:454:10
208.47:464:10
218.47:474:11
228.47:474:11
238.47:474:11
248.47:484:12
258.47:484:13
268.47:494:13
278.47:494:14
288.47:494:14
298.47:494:15
308.47:504:16
318.57:504:17

Solar energy in December

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in December, about 1.3 kWh/m² — the year's lowest.

For context, solar energy here swings from a low near 1.3 kWh/m² to a high of 7.84 kWh/m² in July across the year — December's 1.3 kWh/m² sits near the bottom.

00.511.52151015202531
Solar energy (kWh/m²)Level
11.4Dim
21.4Dim
31.4Dim
41.4Dim
51.4Dim
61.4Dim
71.3Dim
81.3Dim
91.3Dim
101.3Dim
111.3Dim
121.3Dim
131.3Dim
141.3Dim
151.3Dim
161.3Dim
171.3Dim
181.3Dim
191.3Dim
201.3Dim
211.3Dim
221.3Dim
231.3Dim
241.3Dim
251.3Dim
261.3Dim
271.3Dim
281.3Dim
291.3Dim
301.3Dim
311.3Dim
Planning a trip in December

Is December a good time to visit Sunnyside?

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

0.0
Sightseeing
12th-best month of the year
0.0
Beach & pool
10th-best month of the year

December is a weaker month for outdoor sightseeing in Sunnyside.

What to pack for Sunnyside in December

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

In December, Sunnyside sees daytime highs around 39°F and nights near 28°F. Pack a warm layer. Worth having: a heavy coat and rain gear. About 9 days see rain.

a warm layera heavy coatrain gear

UV index in Sunnyside 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 Sunnyside peaks around July 16 at about 8 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 14 at about 1 (low).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighHighVery highHighModerateLowJul 16UV 8Dec 14UV 1
UV index (midday)Level
Jan1Low
Feb2Low
Mar4Moderate
Apr5High
May7Very high
Jun6High
Jul9Very high
Aug6High
Sep5Moderate
Oct4Moderate
Nov1Low
Dec1Low

Air quality in Sunnyside 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 Sunnyside is worst in August — around 30 µg/m³ PM2.5 (moderate), about 4.0× the cleanest month (December, 7 µg/m³).

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

010203040JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodAug 2029 µg/m³Dec 178 µg/m³
PM2.5 (µg/m³)Level
Jan9Good
Feb10Good
Mar12Good
Apr10Good
May9Good
Jun10Good
Jul13Moderate
Aug30Moderate
Sep23Moderate
Oct10Good
Nov10Good
Dec7Good
Location & terrain

Where is Sunnyside?

Sunnyside sits at 46.3°N, 120.0°W, 745 ft above sea level, in United States. The nearest listed city is Yakima, 30 mi away.

Topography around Sunnyside

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

Within 2 miles, the terrain around Sunnyside has only modest variations in elevation — a maximum elevation change of 289 ft around an average of 764 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 2,152 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 5,568 ft.

The land around Sunnyside is covered by cropland (34%), grassland (29%) and artificial surfaces (24%) within 2 miles, grassland (46%) and cropland (38%) within 10 miles, and grassland (62%) and cropland (24%) within 50 miles.

2 miles
289 ft
10 miles
2,152 ft
50 miles
5,568 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
December weather nearby: Yakima 30 mi · Richland 35 mi · Tri-Cities 39 mi · Kennewick 42 mi · Pasco 43 mi · Hermiston 48 mi · Ellensburg 53 mi · Moses Lake 66 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 Sunnyside (46.3237°, -120.0087°, elevation 745 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. 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).