San Marcos weather in May

In May, San Marcos sees average daytime highs of 85°F and overnight lows near 66°F, with 4.5 in of rain across 11.4 wet days and about 13.5 hours of daylight. It is the 5th-warmest and 1st-wettest month of the year here.

Highs climb over the month, from about 82°F in the first days to 88°F by the end. The sky is clear or mostly clear about 31% of the time in May, and the air most often feels muggy.

Daylight stretches from about 13 h 06 min at the start of May to 13 h 48 min by month's end. Set against the rest of the year, May is San Marcos's 12th-clearest and 3rd-windiest month. For the whole year in context, see San Marcos's year-round climate.

Daytime high
85°
5th warmest
Overnight low
66°
8th coldest
Rainfall
4.5 in
11.4 wet days
Daylight
13 h 30 min
5:43 AM – 7:13 PM
Cloud cover
57%
12th clearest
Wind
8 mph
3rd windiest
Solar energy
5.67 kWh/m²
Travel score
5.3
out of 10

San Marcos is city in and county seat of Hays County, Texas, United States, that extends into Caldwell and Guadalupe counties.

Density
684/km²
people per km²
Founded
1808

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 82°F in the first days to 88°F by the end.

A typical May day in San Marcos reaches about 85°F in the afternoon and slips back to 66°F overnight — a 18°F spread between the day's warmth and the night's chill. On most days the high lands between 77°F and 92°F. Set against its neighbours, May runs about 6°F warmer than April and about 6°F cooler than June.

50°60°70°80°90°151015202531
Avg high (°F)Avg low (°F)
18262
28263
38263
48263
58264
68364
78364
88364
98365
108365
118365
128465
138466
148466
158466
168466
178567
188567
198567
208567
218568
228668
238668
248668
258769
268769
278769
288769
298869
308870
318870

How May really feels in San Marcos

Once humidity and wind are folded in, May averages 5 days that feel above 90°F and 0 that feel at or below 32°F — the comfort signal a plain temperature reading hides.

Days feeling ≥ 90°F
5
heat index over the day's high
Days feeling ≤ 32°F
0
wind chill below the day's low

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

San Marcos weather by month

How May compares with the rest of the year at a glance. May is the 5th-warmest and 1st-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysDaylight (hours)Travel score
Jan61° / 42°2.57.410.35.4
Feb65° / 46°2.47.610.96.2
Mar71° / 52°3.09.411.86.8
Apr78° / 59°3.3912.76.9
May85° / 66°4.511.413.55.3
Jun90° / 72°3.29.813.93.9
Jul94° / 74°1.86.413.73.2
Aug94° / 74°2.46.413.13.0
Sep88° / 69°3.08.212.24.7
Oct80° / 60°3.27.511.37.1
Nov69° / 50°2.8710.57.0
Dec62° / 43°2.87.910.15.7

Cloud cover in May

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 31% of the time in May, the cloudiest month of the year.

Beyond those clear spells, partly cloudy skies cover about 20% of May, with mostly cloudy or overcast conditions the remaining 50%.

0%25%50%75%100%151015202531
Clearer (%)Cloudier (%)
14951
24852
34753
44753
54753
64654
74654
84654
94654
104654
114852
124852
134852
144951
155050
165050
175050
185149
195149
205248
215149
225248
235347
245248
255347
265347
275446
285446
295545
305743
315842

Chance of precipitation in May

Any precipitation

San Marcos gets around 4.5 in of rain over 11.4 wet days in May, the wettest month. 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 37% on the wettest days.

0%10%20%30%40%50%151015202531
Rain chance (%)
134
235
335
436
536
637
737
837
937
1037
1137
1237
1336
1436
1536
1636
1736
1836
1936
2036
2136
2236
2337
2437
2537
2636
2736
2836
2936
3035
3135

Humidity in May

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, May lands in the muggy band about 44% of days. Sticky, muggy-or-worse air turns up on roughly 61% of them.

0%25%50%75%100%151015202531
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
1291222317
2271222328
3261122338
4251121349
52410213510
62210213611
72110213712
82010203712
91910203813
101710203914
111610204014
121510204015
131410204115
141310204216
15129194316
16119194417
17108194517
1898194618
1998184718
2087184919
2177175019
2266175120
2356175121
2445165322
2545165223
2634155424
2724155425
2824145426
2914135527
3013135528
3113125430

Wind in May

Winds average 8 mph in May.

Across May, daily wind ranges from about 8 mph on the calmest days to 9 mph at its breeziest. It stays fairly steady from day to day.

051015151015202531
Wind speed (mph)Feels
19light breeze
29light breeze
39light breeze
49light breeze
59light breeze
69light breeze
79light breeze
89light breeze
99light breeze
109light breeze
118light breeze
128light breeze
138light breeze
148light breeze
158light breeze
168light breeze
178light breeze
188light breeze
198light breeze
208light breeze
218light breeze
228light breeze
238light breeze
248light breeze
258light breeze
268light breeze
278light breeze
288light breeze
298light breeze
308light breeze
318light breeze

Sunrise & sunset in May

DaylightNight

Daylight runs from about 13 h 06 min at the start of May to 13 h 48 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 42 minutes over May. Sunrise moves from 5:55 AM to 5:36 AM, and sunset from 7:03 PM to 7:22 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202531
Daylight (h)Sunrise (AM)Sunset (PM)
113.15:557:03
213.25:547:04
313.25:537:04
413.25:527:05
513.25:517:06
613.35:507:06
713.35:507:07
813.35:497:08
913.35:487:08
1013.45:477:09
1113.45:467:10
1213.45:467:10
1313.45:457:11
1413.55:447:12
1513.55:447:12
1613.55:437:13
1713.55:427:14
1813.55:427:14
1913.65:417:15
2013.65:417:15
2113.65:407:16
2213.65:407:17
2313.65:397:17
2413.75:397:18
2513.75:387:19
2613.75:387:19
2713.75:387:20
2813.75:377:20
2913.75:377:21
3013.75:377:21
3113.85:367:22

Solar energy in May

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in May, about 5.67 kWh/m².

For context, solar energy here swings from a low near 2.69 kWh/m² to a high of 6.69 kWh/m² in July across the year — May's 5.67 kWh/m² falls in the middle.

0246151015202531
Solar energy (kWh/m²)Level
15.6Bright
25.6Bright
35.6Bright
45.6Bright
55.6Bright
65.6Bright
75.6Bright
85.6Bright
95.6Bright
105.6Bright
115.6Bright
125.6Bright
135.7Bright
145.7Bright
155.7Bright
165.7Bright
175.7Bright
185.7Bright
195.8Bright
205.8Bright
215.8Bright
225.8Bright
235.8Bright
245.8Bright
255.9Bright
265.9Bright
275.9Bright
286.0Bright
296.0Bright
306.0Intense
316.1Intense
Planning a trip in May

Is May a good time to visit San Marcos?

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

5.3
Sightseeing
8th-best month of the year
6.7
Beach & pool
3rd-best month of the year

May is a reasonable time to visit San Marcos for sightseeing. The water and warmth also suit a beach or pool day.

What to pack for San Marcos in May

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

In May, San Marcos sees daytime highs around 85°F and nights near 66°F. Pack light clothes. Worth having: rain gear and sun protection. About 11 days see rain.

light clothesrain gearsun protection

UV index in San Marcos in May

LowModerateHighVery highExtreme

Clear-sky midday UV in May peaks around 10 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in San Marcos peaks around August 11 at about 11 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 20 at about 4 (moderate).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highExtremeVery highHighModerateAug 11UV 11Dec 20UV 4
UV index (midday)Level
Jan4Moderate
Feb6High
Mar7High
Apr10Very high
May10Extreme
Jun10Extreme
Jul10Extreme
Aug11Extreme
Sep9Very high
Oct6High
Nov5Moderate
Dec4Moderate

Air quality in San Marcos 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 San Marcos is worst in July — around 17 µg/m³ PM2.5 (moderate), about 2.9× the cleanest month (December, 6 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1416 µg/m³Dec 136 µg/m³
PM2.5 (µg/m³)Level
Jan6Good
Feb7Good
Mar8Good
Apr9Good
May14Moderate
Jun14Moderate
Jul17Moderate
Aug12Good
Sep10Good
Oct6Good
Nov6Good
Dec6Good
Location & terrain

Where is San Marcos?

San Marcos sits at 29.9°N, 97.9°W, 617 ft above sea level, in United States. The nearest listed city is Kyle, 8.1 mi away.

Topography around San Marcos

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

Within 2 miles, the terrain around San Marcos has only modest variations in elevation — a maximum elevation change of 289 ft around an average of 643 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 751 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 1,814 ft.

The land around San Marcos is covered by trees (42%), artificial surfaces (31%) and grassland (23%) within 2 miles, trees (41%) and grassland (39%) within 10 miles, and trees (48%) and grassland (42%) within 50 miles.

2 miles
289 ft
10 miles
751 ft
50 miles
1,814 ft
treesgrasslandcroplandartificial surfacesbare terrainwater
May weather nearby: Kyle 8.1 mi · New Braunfels 17 mi · Canyon Lake 19 mi · Seguin 22 mi · Cibolo 28 mi · Austin 29 mi · Schertz 30 mi · University of Texas 30 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 San Marcos (29.8833°, -97.9414°, elevation 617 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).