Climate and average weather in San Marcos
In San Marcos, the summers are humid, sweltering, fairly dry, and mostly clear and the winters are mild and partly cloudy.
Over the course of the year, the temperature in San Marcos typically varies from 42°F to 94°F, and is rarely below 30°F or above 100°F. August is the hottest month of the year, while January is the coldest.
Based on the travel score, the best times of year to visit San Marcos for warm-weather activities are from early February to early May and late September to mid December.
- Hottest
- Aug
- 94°
- Coldest
- Jan
- 42°
- Wettest
- May
- 4.5 in
- Driest
- Jul
- 1.8 in
- Rain / yr
- 34.9 in
- 98 wet days
- Daylight
- 10.1–13.9 h
- shortest–longest
- Elevation
- 617 ft
- 29.9°N
- Clearest
- Oct
- 41% cloud
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.
San Marcos weather by month, at a glance
The whole year in one picture — sky, rain, humidity, temperature and travel score. Click any band to jump to its full chart.
Each stripe is one measure across the whole year, stacked so a single day reads top to bottom. The sky band runs overcast grey on top down to clear blue at the base — more blue means sunnier — followed by the rainfall curve, the humidity band, a temperature strip that tints each stretch of the year by how warm its average high is, and the travel-score line at the foot. Scan straight down any date to read that day across every measure at once; the score climbs highest around early February to early May.
Temperature through the year
Daily average highs and lows in San Marcos, from 1991–2020 of climate data. The shaded bands show the range most days fall in — 10th to 90th percentile.
The hot season lasts 4.0 months, from May 25 to September 24, with daily high temperatures above 87°F. The hottest month of the year in San Marcos is August, with an average high of 94°F and low of 74°F.
The cool season lasts 3.1 months, from November 25 to February 25, with daily high temperatures below 67°F. The coldest month of the year in San Marcos is January, with an average low of 42°F and high of 61°F.
Days typically run about 19°F warmer than nights year-round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°F) | 61 | 65 | 71 | 78 | 85 | 90 | 94 | 94 | 88 | 80 | 69 | 62 |
| Avg low (°F) | 42 | 46 | 52 | 59 | 66 | 72 | 74 | 74 | 69 | 60 | 50 | 43 |
| Avg high (°F) | Avg low (°F) | |
|---|---|---|
| Jan | 61 | 42 |
| Feb | 65 | 46 |
| Mar | 71 | 52 |
| Apr | 78 | 59 |
| May | 85 | 66 |
| Jun | 90 | 72 |
| Jul | 94 | 74 |
| Aug | 94 | 74 |
| Sep | 88 | 69 |
| Oct | 80 | 60 |
| Nov | 69 | 50 |
| Dec | 62 | 43 |
How hot and cold San Marcos really feels
The felt-temperature range through the year — heat index on the day's high (summer humidity), wind chill on the night's low (winter wind). The dashed lines are the plain thermometer; the gap is how much hotter or colder it really feels.
On the hottest afternoons, once humidity is folded in, San Marcos feels like about 101°F (around August 6). About 115 days a year carry some heat stress, peaking in August.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Feels-like high (°F) | 61 | 65 | 71 | 78 | 86 | 95 | 99 | 99 | 91 | 80 | 70 | 62 |
| Air high (°F) | 61 | 65 | 71 | 78 | 85 | 90 | 94 | 94 | 88 | 80 | 69 | 62 |
| Feels-like low (°F) | 37 | 41 | 51 | 59 | 66 | 72 | 74 | 74 | 69 | 60 | 49 | 39 |
| Air low (°F) | 42 | 46 | 52 | 59 | 66 | 72 | 74 | 74 | 69 | 60 | 50 | 43 |
| Feels-like high (°F) | Air high (°F) | Feels-like low (°F) | Air low (°F) | |
|---|---|---|---|---|
| Jan | 61 | 61 | 37 | 42 |
| Feb | 65 | 65 | 41 | 46 |
| Mar | 71 | 71 | 51 | 52 |
| Apr | 78 | 78 | 59 | 59 |
| May | 86 | 85 | 66 | 66 |
| Jun | 95 | 90 | 72 | 72 |
| Jul | 99 | 94 | 74 | 74 |
| Aug | 99 | 94 | 74 | 74 |
| Sep | 91 | 88 | 69 | 69 |
| Oct | 80 | 80 | 60 | 60 |
| Nov | 70 | 69 | 49 | 50 |
| Dec | 62 | 62 | 39 | 43 |
Average hourly temperature in San Marcos
A compact picture of the whole year, hour by hour: each column is a day, each row an hour, and the color is the modeled average temperature. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
Read left to right for the day of the year and top to bottom for the hour of the day; the color is the modeled temperature, cool blues through to hot reds on the same scale as the other charts. A vertical slice is a single day's swing — coolest just before dawn, warmest in the mid-afternoon — while a horizontal slice follows one hour across the seasons. The darker overlay marks night and the lighter one the twilight around sunrise and sunset. Colors run warmest on August afternoons, near 94°F, and coldest before dawn in January, near 42°F.
San Marcos weather by month
Every month at a glance. Click a month for its detailed page.
| Month | High / Low (°F) | Rainfall (inches) | Wet days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|
| Jan | 61° / 42° | 2.5 | 7.4 | 10.3 | 5.4 |
| Feb | 65° / 46° | 2.4 | 7.6 | 10.9 | 6.2 |
| Mar | 71° / 52° | 3.0 | 9.4 | 11.8 | 6.8 |
| Apr | 78° / 59° | 3.3 | 9 | 12.7 | 6.9 |
| May | 85° / 66° | 4.5 | 11.4 | 13.5 | 5.3 |
| Jun | 90° / 72° | 3.2 | 9.8 | 13.9 | 3.9 |
| Jul | 94° / 74° | 1.8 | 6.4 | 13.7 | 3.2 |
| Aug | 94° / 74° | 2.4 | 6.4 | 13.1 | 3.0 |
| Sep | 88° / 69° | 3.0 | 8.2 | 12.2 | 4.7 |
| Oct | 80° / 60° | 3.2 | 7.5 | 11.3 | 7.1 |
| Nov | 69° / 50° | 2.8 | 7 | 10.5 | 7.0 |
| Dec | 62° / 43° | 2.8 | 7.9 | 10.1 | 5.7 |
Chance of rain
How likely it is to rain on a typical day, and how that shifts across the wetter and drier seasons.
San Marcos gets about 34.9 in of precipitation a year. On a typical day the chance of rain is some rain, but that rises and falls sharply with the seasons.
The wetter season lasts 4.8 months, from around Feb 10 to Jul 5, peaking in May at about 36% chance on a given day. The drier stretch runs the rest of the year, bottoming out around Jul 30.
May is the wettest month by volume, with 4.5 in over about 11 wet days; July is the driest, with 1.8 in.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rain on a day (%) | 24 | 27 | 30 | 30 | 36 | 33 | 21 | 21 | 27 | 24 | 24 | 25 |
| Rain days | 7 | 8 | 9 | 9 | 11 | 10 | 6 | 6 | 8 | 8 | 7 | 8 |
| Rain on a day (%) | Rain days | |
|---|---|---|
| Jan | 24 | 7 |
| Feb | 27 | 8 |
| Mar | 30 | 9 |
| Apr | 30 | 9 |
| May | 36 | 11 |
| Jun | 33 | 10 |
| Jul | 21 | 6 |
| Aug | 21 | 6 |
| Sep | 27 | 8 |
| Oct | 24 | 8 |
| Nov | 24 | 7 |
| Dec | 25 | 8 |
Monthly rainfall
Over a full year, San Marcos collects about 34.9 in of rain across 98 wet days — roughly 2.9 in in an average month.
It doesn’t fall evenly. May is the wettest month with 4.5 in, while July is the driest at just 1.8 in. The three wettest months alone bring about 32% of the year’s total.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rainfall (in) | 2.5 | 2.4 | 3.0 | 3.3 | 4.5 | 3.2 | 1.8 | 2.4 | 3.0 | 3.2 | 2.8 | 2.8 |
| Rain days | 7 | 8 | 9 | 9 | 11 | 10 | 6 | 6 | 8 | 8 | 7 | 8 |
| Rainfall (in) | Rain days | |
|---|---|---|
| Jan | 2.5 | 7 |
| Feb | 2.4 | 8 |
| Mar | 3.0 | 9 |
| Apr | 3.3 | 9 |
| May | 4.5 | 11 |
| Jun | 3.2 | 10 |
| Jul | 1.8 | 6 |
| Aug | 2.4 | 6 |
| Sep | 3.0 | 8 |
| Oct | 3.2 | 8 |
| Nov | 2.8 | 7 |
| Dec | 2.8 | 8 |
Clouds and sunshine
How often the daytime sky is clear, partly cloudy or overcast.
In San Marcos, the average share of the sky covered by clouds shows moderate seasonal variation over the course of the year.
The clearer part of the year begins around May 31 and lasts for 5.3 months, ending around November 7. The clearest month is August, when the sky is clear, mostly clear, or partly cloudy 71% of the time on average.
The cloudier part of the year begins around November 8 and lasts for 6.7 months, ending around May 30. The cloudiest month is March, when it is overcast or mostly cloudy 52% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 49 | 49 | 48 | 52 | 51 | 65 | 68 | 71 | 68 | 68 | 58 | 50 |
| Cloudier (%) | 51 | 51 | 52 | 48 | 49 | 35 | 32 | 29 | 32 | 32 | 42 | 50 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| Jan | 49 | 51 |
| Feb | 49 | 51 |
| Mar | 48 | 52 |
| Apr | 52 | 48 |
| May | 51 | 49 |
| Jun | 65 | 35 |
| Jul | 68 | 32 |
| Aug | 71 | 29 |
| Sep | 68 | 32 |
| Oct | 68 | 32 |
| Nov | 58 | 42 |
| Dec | 50 | 50 |
Daylight, sunrise and sunset
Hours of daylight through the year, with sunrise and sunset times.
The gold band is daylight — sunrise runs along its lower edge, sunset along the upper — so it widens toward summer and pinches toward winter, with night the dark area above and below. The longest day, around June 8, brings about 13 h 54 min of light; the shortest, around January 1, only 10 h 06 min — a swing of roughly 3 h 48 min.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 10.3 | 10.9 | 11.8 | 12.7 | 13.5 | 13.9 | 13.7 | 13.1 | 12.2 | 11.3 | 10.5 | 10.1 |
| Sunrise (AM) | 7:33 | 7:19 | 6:48 | 6:10 | 5:43 | 5:35 | 5:45 | 6:03 | 6:21 | 6:39 | 7:03 | 7:25 |
| Sunset (PM) | 5:49 | 6:14 | 6:35 | 6:54 | 7:13 | 7:29 | 7:30 | 7:08 | 6:31 | 5:55 | 5:31 | 5:31 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| Jan | 10.3 | 7:33 | 5:49 |
| Feb | 10.9 | 7:19 | 6:14 |
| Mar | 11.8 | 6:48 | 6:35 |
| Apr | 12.7 | 6:10 | 6:54 |
| May | 13.5 | 5:43 | 7:13 |
| Jun | 13.9 | 5:35 | 7:29 |
| Jul | 13.7 | 5:45 | 7:30 |
| Aug | 13.1 | 6:03 | 7:08 |
| Sep | 12.2 | 6:21 | 6:31 |
| Oct | 11.3 | 6:39 | 5:55 |
| Nov | 10.5 | 7:03 | 5:31 |
| Dec | 10.1 | 7:25 | 5:31 |
Sunny days
How many genuinely sunny days each month brings — days the sky stays clear or mostly clear — banded into plain-language zones.
San Marcos averages about 13 sunny days a month — counting the days the sky stays clear or mostly clear — with a clear seasonal swing between 9 and 17 days.
The sunnier stretch runs 5.6 months, from around Jun 11 to Nov 27. The sunniest month is September, with roughly 15 sunny days (bright).
The greyest month is May, down near 9 sunny days — about 38% fewer than the September peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sunny days | 12 | 11 | 11 | 11 | 10 | 13 | 15 | 16 | 15 | 16 | 13 | 12 |
| Sky | Mixed | Mixed | Mixed | Mixed | Mixed | Mixed | Mixed | Bright | Bright | Bright | Mixed | Mixed |
| Sunny days | Sky | |
|---|---|---|
| Jan | 12 | Mixed |
| Feb | 11 | Mixed |
| Mar | 11 | Mixed |
| Apr | 11 | Mixed |
| May | 10 | Mixed |
| Jun | 13 | Mixed |
| Jul | 15 | Mixed |
| Aug | 16 | Bright |
| Sep | 15 | Bright |
| Oct | 16 | Bright |
| Nov | 13 | Mixed |
| Dec | 12 | Mixed |
Humidity comfort
Share of days at each humidity comfort level, based on the dew point — the measure that tracks how muggy it actually feels.
Humidity comfort is graded by the dew point — the temperature at which the air would be fully saturated — because it tracks how muggy it actually feels far better than relative humidity does. A low dew point feels dry and crisp; a high one feels sticky and oppressive no matter the reading on a humidity gauge.
In San Marcos, how humid it feels changes dramatically over the year.
The more humid part of the year lasts 5.6 months, from around April 24 to October 11. The muggiest month is July, when the air feels humid, muggy or worse about 99% of the time.
The most comfortable stretch runs from around October 12 to April 23, and January is the most comfortable month — the air is dry or comfortable 94% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Dry (%) | 87 | 81 | 61 | 40 | 13 | 1 | 1 | 0 | 11 | 37 | 64 | 82 |
| Comfortable (%) | 7 | 10 | 16 | 16 | 8 | 2 | 1 | 3 | 10 | 16 | 13 | 8 |
| Humid (%) | 5 | 8 | 18 | 22 | 18 | 9 | 7 | 10 | 15 | 17 | 13 | 7 |
| Muggy (%) | 1 | 1 | 6 | 21 | 44 | 40 | 44 | 50 | 32 | 19 | 9 | 2 |
| Oppressive (%) | 0 | 0 | 0 | 2 | 17 | 47 | 47 | 37 | 33 | 10 | 1 | 0 |
| Miserable (%) | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | 0 | 0 | 0 |
| Dry (%) | Comfortable (%) | Humid (%) | Muggy (%) | Oppressive (%) | Miserable (%) | |
|---|---|---|---|---|---|---|
| Jan | 87 | 7 | 5 | 1 | 0 | 0 |
| Feb | 81 | 10 | 8 | 1 | 0 | 0 |
| Mar | 61 | 16 | 18 | 6 | 0 | 0 |
| Apr | 40 | 16 | 22 | 21 | 2 | 0 |
| May | 13 | 8 | 18 | 44 | 17 | 0 |
| Jun | 1 | 2 | 9 | 40 | 47 | 1 |
| Jul | 1 | 1 | 7 | 44 | 47 | 0 |
| Aug | 0 | 3 | 10 | 50 | 37 | 1 |
| Sep | 11 | 10 | 15 | 32 | 33 | 0 |
| Oct | 37 | 16 | 17 | 19 | 10 | 0 |
| Nov | 64 | 13 | 13 | 9 | 1 | 0 |
| Dec | 82 | 8 | 7 | 2 | 0 | 0 |
Wind
Average wind speed through the year, banded into plain-language speed zones so a number reads as 'breezy' or 'calm' without knowing the scale.
This is the average sustained wind speed at the standard 10 metres above open ground — the steady flow a weather station reports, not the sharper gusts that come and go, which can run half again as fast. It's the number that says whether a place is generally breezy or calm.
Across the year, average wind speed in San Marcos is typically light breeze, near 8 mph, and varies little with the seasons.
The windier part of the year lasts 7.4 months, from around Nov 1 to Jun 13. The windiest month is April, averaging about 9 mph (light breeze).
The calmer part of the year runs from around Jun 14 to Oct 31, with September the calmest month at about 6 mph.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (mph) | 8 | 8 | 8 | 9 | 8 | 8 | 7 | 6 | 6 | 7 | 8 | 8 |
| Feels | light breeze | light breeze | light breeze | light breeze | light breeze | light breeze | calm | calm | calm | calm | light breeze | light breeze |
| Wind speed (mph) | Feels | |
|---|---|---|
| Jan | 8 | light breeze |
| Feb | 8 | light breeze |
| Mar | 8 | light breeze |
| Apr | 9 | light breeze |
| May | 8 | light breeze |
| Jun | 8 | light breeze |
| Jul | 7 | calm |
| Aug | 6 | calm |
| Sep | 6 | calm |
| Oct | 7 | calm |
| Nov | 8 | light breeze |
| Dec | 8 | light breeze |
Best time to visit San Marcos
To characterize how pleasant the weather is in San Marcos throughout the year, we compute two travel scores — one for general sightseeing, one for beach and pool weather.
Around mid February, San Marcos is still near the start of its best-weather window — great conditions with the peak-season crowds not yet at full swing.
Inferred from the travel-score curve; month-by-month visitor numbers are a planned addition.
The travel score favors clear, rainless days with daytime highs between 64°F and 82°F. Based on this score, the best times of year to visit San Marcos for general outdoor tourist activities run from mid February to early May and again from early October to mid December, with a peak score in the last week of October.
The travel score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Travel score (0–10) | 5.4 | 6.2 | 6.8 | 6.9 | 5.3 | 3.9 | 3.2 | 3.0 | 4.7 | 7.0 | 7.0 | 5.8 |
| Rating | fair | good | good | good | fair | fair | poor | poor | fair | good | good | good |
| Travel score (0–10) | Rating | |
|---|---|---|
| Jan | 5.4 | fair |
| Feb | 6.2 | good |
| Mar | 6.8 | good |
| Apr | 6.9 | good |
| May | 5.3 | fair |
| Jun | 3.9 | fair |
| Jul | 3.2 | poor |
| Aug | 3.0 | poor |
| Sep | 4.7 | fair |
| Oct | 7.0 | good |
| Nov | 7.0 | good |
| Dec | 5.8 | good |
The beach/pool score favors clear, rainless days with daytime highs between 75°F and 93°F. Based on this score, the best times of year to visit San Marcos for hot-weather activities run from early April to early August and again from mid August to late October, with a peak score in the first week of October.
The beach/pool score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
What to pack for San Marcos, by month
Month by month, what's worth putting in the bag — from the temperature range, rain chance, sun and wind. Tap a month for a quick packing note.
For a warm-season trip around August (highs near 94°F), the essentials are light clothes and sun protection. In the cold season around January (highs near 61°F), pack a warm layer.
In August, San Marcos sees daytime highs around 94°F and nights near 74°F. Pack light clothes and sun protection. About 6 days see rain.
UV index (midday) in San Marcos by month
Clear-sky midday UV index through the year, shaded by the WHO exposure levels — how much sun protection each month calls for.
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.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 4 | 6 | 7 | 10 | 10 | 10 | 10 | 11 | 9 | 6 | 5 | 4 |
| Level | Moderate | High | High | Very high | Extreme | Extreme | Extreme | Extreme | Very high | High | Moderate | Moderate |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 4 | Moderate |
| Feb | 6 | High |
| Mar | 7 | High |
| Apr | 10 | Very high |
| May | 10 | Extreme |
| Jun | 10 | Extreme |
| Jul | 10 | Extreme |
| Aug | 11 | Extreme |
| Sep | 9 | Very high |
| Oct | 6 | High |
| Nov | 5 | Moderate |
| Dec | 4 | Moderate |
Average hourly UV index in San Marcos
Modeled clear-sky UV for every hour of every day — when in the day sun protection actually matters.
The whole year hour by hour: each column is a day, each row an hour, and the color is the modeled clear-sky UV index — the midday peak scaled down as the sun sits lower in the sky. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
UV falls off far faster than brightness as the sun drops, so even in August the burn window is concentrated in the middle of the day: about 8 hours a day reach index 3 (protection recommended), and 5.5 hours reach 6 or more. Mornings and late afternoons stay comparatively gentle year round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV ≥ 3 (h/day) | 4 | 5.5 | 6.5 | 7.5 | 8.5 | 8.5 | 8.5 | 8 | 7 | 6 | 4.5 | 3 |
| UV ≥ 6 (h/day) | 0 | 0 | 3 | 5.5 | 6 | 6 | 6 | 5.5 | 4.5 | 2 | 0 | 0 |
| UV ≥ 3 (h/day) | UV ≥ 6 (h/day) | |
|---|---|---|
| Jan | 4 | 0 |
| Feb | 5.5 | 0 |
| Mar | 6.5 | 3 |
| Apr | 7.5 | 5.5 |
| May | 8.5 | 6 |
| Jun | 8.5 | 6 |
| Jul | 8.5 | 6 |
| Aug | 8 | 5.5 |
| Sep | 7 | 4.5 |
| Oct | 6 | 2 |
| Nov | 4.5 | 0 |
| Dec | 3 | 0 |
Air quality in San Marcos by month
Average fine-particle pollution (PM2.5) through the year — so you can see which months the air is worst, not just the yearly 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).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 6 | 7 | 8 | 9 | 14 | 14 | 17 | 12 | 10 | 6 | 6 | 6 |
| Level | Good | Good | Good | Good | Moderate | Moderate | Moderate | Good | Good | Good | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 6 | Good |
| Feb | 7 | Good |
| Mar | 8 | Good |
| Apr | 9 | Good |
| May | 14 | Moderate |
| Jun | 14 | Moderate |
| Jul | 17 | Moderate |
| Aug | 12 | Good |
| Sep | 10 | Good |
| Oct | 6 | Good |
| Nov | 6 | Good |
| Dec | 6 | Good |
Growing season
San Marcos is mild enough that a frost-free day stays more likely than not even in midwinter. Nights are reliably above freezing from about February 11 to December 3 (296 days); outside that window a hard frost is an occasional risk.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Frost-free chance (%) | 86 | 91 | 98 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 96 | 88 |
| Frost nights | 31 | 8 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 15 |
| Frost-free chance (%) | Frost nights | |
|---|---|---|
| Jan | 86 | 31 |
| Feb | 91 | 8 |
| Mar | 98 | 0 |
| Apr | 100 | 0 |
| May | 100 | 0 |
| Jun | 100 | 0 |
| Jul | 100 | 0 |
| Aug | 100 | 0 |
| Sep | 100 | 0 |
| Oct | 100 | 0 |
| Nov | 96 | 0 |
| Dec | 88 | 15 |
Growing degree days
Growing degree days tally heat above 50°F: each day adds however many degrees its average temperature runs over that threshold, and cold days add nothing. San Marcos banks about 6,801 degree days a year, and the running total — which growers use to time plantings and predict maturity — climbs fastest around August.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Growing degree days (°F·days) | 44 | 146 | 364 | 552 | 789 | 937 | 1,048 | 1,059 | 862 | 617 | 298 | 87 |
| Growing degree days (°F·days) | |
|---|---|
| Jan | 44 |
| Feb | 146 |
| Mar | 364 |
| Apr | 552 |
| May | 789 |
| Jun | 937 |
| Jul | 1,048 |
| Aug | 1,059 |
| Sep | 862 |
| Oct | 617 |
| Nov | 298 |
| Dec | 87 |
Solar energy
Average daily shortwave solar energy reaching the ground, banded into brightness zones so the number means something at a glance.
Solar energy is how much sunlight actually reaches the ground each day, measured in kilowatt-hours per square metre (kWh/m²) — the combined effect of how long the sun is up, how high it climbs, and how much cloud gets in the way. It's the raw fuel a solar panel has to work with: for scale, 1 kWh/m² a day is dim and wintry, while 7+ is desert-bright.
San Marcos receives about 4.7 kWh/m² a day of solar energy on average — bright — with a clear seasonal swing between 2.7 and 6.8 kWh/m².
The brighter stretch of the year lasts 6.3 months, from around Mar 26 to Oct 2. The brightest month is July, averaging about 6.7 kWh/m² (intense).
The dimmest month is December, down near 2.7 kWh/m² — roughly 59% less than the July peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 3.0 | 3.5 | 4.4 | 5.5 | 5.7 | 6.3 | 6.7 | 6.3 | 5.2 | 4.1 | 3.1 | 2.7 |
| Level | Moderate | Moderate | Bright | Bright | Bright | Intense | Intense | Intense | Bright | Bright | Moderate | Moderate |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| Jan | 3.0 | Moderate |
| Feb | 3.5 | Moderate |
| Mar | 4.4 | Bright |
| Apr | 5.5 | Bright |
| May | 5.7 | Bright |
| Jun | 6.3 | Intense |
| Jul | 6.7 | Intense |
| Aug | 6.3 | Intense |
| Sep | 5.2 | Bright |
| Oct | 4.1 | Bright |
| Nov | 3.1 | Moderate |
| Dec | 2.7 | Moderate |
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.
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
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).