Vacaville weather in May

In May, Vacaville sees average daytime highs of 77°F and overnight lows near 53°F, with 0.7 in of rain across 3.2 wet days and about 14.1 hours of daylight. It is the 5th-warmest and 8th-wettest month of the year here.

Highs climb over the month, from about 75°F in the first days to 79°F by the end. The sky is clear or mostly clear about 57% of the time in May, and the air most often feels dry.

Daylight stretches from about 13 h 36 min at the start of May to 14 h 24 min by month's end. Set against the rest of the year, May is Vacaville's 6th-clearest and 3rd-windiest month. For the whole year in context, see Vacaville's year-round climate.

Daytime high
77°
5th warmest
Overnight low
53°
8th coldest
Rainfall
0.7 in
3.2 wet days
Daylight
14 h 06 min
5:02 AM – 7:06 PM
Cloud cover
37%
6th clearest
Wind
7 mph
3rd windiest
Solar energy
7.28 kWh/m²
Travel score
8.4
out of 10

Vacaville is city in Solano County, California, United States of America.

Density
1,308/km²
people per km²
Founded
1852

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

Temperature in May

Average highAverage lowShaded bands: 10–90% of days

Highs climb over the month, from about 75°F in the first days to 79°F by the end.

A typical May day in Vacaville reaches about 77°F in the afternoon and slips back to 53°F overnight — a 24°F spread between the day's warmth and the night's chill. On most days the high lands between 67°F and 88°F. Set against its neighbours, May runs about 6°F warmer than April and about 6°F cooler than June.

40°60°80°151015202531
Avg high (°F)Avg low (°F)
17551
27552
37552
47552
57652
67652
77652
87652
97652
107653
117653
127653
137653
147653
157753
167753
177753
187753
197753
207754
217854
227854
237854
247854
257854
267854
277955
287955
297955
308055
318055

Vacaville weather by month

How May compares with the rest of the year at a glance. May is the 5th-warmest and 8th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysDaylight (hours)Travel score
Jan58° / 42°4.39.29.64.3
Feb62° / 44°4.2910.55.2
Mar66° / 46°3.18.211.76.4
Apr71° / 49°1.34.8137.5
May77° / 53°0.73.214.18.4
Jun83° / 57°0.20.914.67.7
Jul85° / 58°0.00.114.47.1
Aug85° / 58°0.00.213.57.1
Sep84° / 57°0.10.412.37.7
Oct77° / 53°0.92.7118.5
Nov65° / 47°2.05.89.96.6
Dec58° / 42°3.999.44.3

Cloud cover in May

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 57% of the time in May.

Beyond those clear spells, partly cloudy skies cover about 15% of May, with mostly cloudy or overcast conditions the remaining 28%. Skies tend to open up as the month goes on.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
16733
26733
36832
46832
56931
66931
76931
86931
97030
107030
117030
127129
137129
147129
157228
167228
177228
187327
197327
207327
217525
227525
237525
247624
257723
267723
277723
287723
297723
307822
317822

Chance of precipitation in May

Any precipitation

Vacaville gets around 0.7 in of rain over 3.2 wet days in May. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 10% and peaks near 12% on the wettest days.

0%10%20%30%151015202531
Rain chance (%)
112
212
311
411
511
611
711
811
911
1011
1111
1211
1311
1411
1511
1611
1711
1811
1910
2010
2110
2210
239
249
258
268
277
287
297
306
316

Humidity in May

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, May lands in the dry band about 94% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)
1964
2964
3964
4964
5964
6964
7964
8964
9964
10964
11964
12964
13964
14964
15964
16964
17955
18955
19955
20946
21946
22937
23928
24928
25919
26919
279010
289010
298911
308911
318911

Wind in May

Winds average 7 mph in May.

Across May, daily wind ranges from about 7 mph on the calmest days to 7 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202531
Wind speed (mph)Feels
17calm
27calm
37calm
47calm
57calm
67calm
77calm
87calm
97calm
107calm
117calm
127calm
137calm
147calm
157calm
167calm
177calm
187calm
197calm
207calm
217calm
227calm
237calm
247calm
257calm
267calm
277calm
287calm
297calm
307calm
317calm

Sunrise & sunset in May

DaylightNight

Daylight runs from about 13 h 36 min at the start of May to 14 h 24 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 48 minutes over May. Sunrise moves from 5:18 AM to 4:52 AM, and sunset from 6:52 PM to 7:19 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
113.65:186:52
213.65:176:53
313.65:156:54
413.75:146:55
513.75:136:56
613.85:126:57
713.85:116:58
813.85:106:59
913.95:097:00
1013.95:087:01
1113.95:077:02
1214.05:067:03
1314.05:057:04
1414.05:047:05
1514.05:037:06
1614.15:027:06
1714.15:017:07
1814.15:007:08
1914.24:597:09
2014.24:597:10
2114.24:587:11
2214.24:577:12
2314.34:567:13
2414.34:567:13
2514.34:557:14
2614.34:557:15
2714.44:547:16
2814.44:537:17
2914.44:537:17
3014.44:527:18
3114.44:527:19

Solar energy in May

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in May, about 7.28 kWh/m².

For context, solar energy here swings from a low near 2.09 kWh/m² to a high of 8.13 kWh/m² in July across the year — May's 7.28 kWh/m² falls in the middle.

02468151015202531
Solar energy (kWh/m²)Level
16.9Intense
26.9Intense
36.9Intense
47.0Intense
57.0Intense
67.0Intense
77.1Intense
87.1Intense
97.1Intense
107.1Intense
117.2Intense
127.2Intense
137.2Intense
147.2Intense
157.3Intense
167.3Intense
177.3Intense
187.3Intense
197.3Intense
207.4Intense
217.4Intense
227.4Intense
237.5Intense
247.5Intense
257.5Intense
267.5Intense
277.6Intense
287.6Intense
297.7Intense
307.7Intense
317.7Intense
Planning a trip in May

Hazard calendar for Vacaville

In seasonPeak

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

Vacaville's rainy season runs November–March, when most of the year's rain falls.

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

Is May a good time to visit Vacaville?

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

8.4
Sightseeing
2nd-best month of the year
7.5
Beach & pool
5th-best month of the year

May is one of the better times to visit Vacaville for general sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Vacaville in May

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

In May, Vacaville sees daytime highs around 77°F and nights near 53°F. Pack sun protection. Worth having: light clothes. About 3 days see rain.

sun protectionlight clothes

UV index in Vacaville in May

LowModerateHighVery highExtreme

Clear-sky midday UV in May peaks around 8 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Vacaville peaks around June 23 at about 10 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 13 at about 2 (moderate).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 9 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateJun 23UV 10Dec 13UV 2
UV index (midday)Level
Jan2Moderate
Feb4Moderate
Mar5Moderate
Apr6High
May8Very high
Jun10Very high
Jul10Very high
Aug9Very high
Sep6High
Oct5Moderate
Nov2Moderate
Dec2Low

Air quality in Vacaville in May

GoodModeratePoorUnhealthyVery unhealthy

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

Air quality in Vacaville is worst in September — around 29 µg/m³ PM2.5 (moderate), about 4.2× the cleanest month (June, 7 µg/m³).

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

010203040JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodModerateSep 1829 µg/m³Jun 127 µg/m³
PM2.5 (µg/m³)Level
Jan13Moderate
Feb13Moderate
Mar13Moderate
Apr10Good
May8Good
Jun7Good
Jul10Good
Aug25Moderate
Sep29Moderate
Oct27Moderate
Nov16Moderate
Dec12Good
Location & terrain

Where is Vacaville?

Vacaville sits at 38.4°N, 122.0°W, 174 ft above sea level, in United States. The nearest listed city is Fairfield, 8.1 mi away.

Topography around Vacaville

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

Within 2 miles, the terrain around Vacaville has only modest variations in elevation — a maximum elevation change of 564 ft around an average of 210 ft above sea level; within 10 miles, large variations in elevation — a maximum elevation change of 2,825 ft; within 50 miles, very significant variations in elevation — a maximum elevation change of 4,459 ft.

The land around Vacaville is covered by artificial surfaces (47%), grassland (25%) and trees (23%) within 2 miles, grassland (41%), trees (25%) and cropland (20%) within 10 miles, and grassland (33%), trees (26%) and cropland (22%) within 50 miles.

2 miles
564 ft
10 miles
2,825 ft
50 miles
4,459 ft
treesgrasslandcroplandartificial surfacesbare terrainwaterwetland
May weather nearby: Fairfield 8.1 mi · Suisun 8.7 mi · Dixon 11 mi · Napa 17 mi · Davis 19 mi · American Canyon 19 mi · Bay Point 22 mi · Vallejo 23 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 Vacaville (38.3566°, -121.9877°, elevation 174 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).