San Marcos (TX) Temperature by Month
The average annual maximum temperature in San Marcos, Texas, United States of America is 27°C (81°F), with daytime highs ranging from 17°C (63°F) in January to 37°C (99°F) in August. This page covers monthly averages, day-night differences, and how San Marcos compares to cities worldwide.
San Marcos Monthly Temperatures
In San Marcos, temperatures differ significantly between summer and winter months. Nighttime lows reflect this range, dropping from 23°C (73°F) in August to 3°C (37°F) in January.
The chart below illustrates the average maximum day and minimum night temperatures in San Marcos by month:
The coldest point of the day usually falls between 4 AM and 6 AM, with temperatures peaking around 3 PM. August, the city's warmest month, gets 298 hours of sunshine.
The chart below shows the average temperature throughout the year:
Temperature: San Marcos vs the United States of America
The map below shows the annual temperature across the United States of America. You can also select individual months if you want to compare a specific time of year.
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San Marcos vs World: Temperature Compared
San Marcos's average annual maximum temperature is 27°C (81°F). To put that in context, here's how it compares to a few well-known destinations:
Athens, Greece sits at 23°C (73°F) on average, with hot dry summers and mild winters characteristic of the Mediterranean.
Zermatt, Switzerland averages just 4°C (39°F) annually due to its altitude, with very cold winters and cool summers even at its warmest.
Seoul, South Korea averages 18°C (64°F) a year, with four clear seasons, cold winters, and hot humid summers.
Perth, Australia averages 25°C (77°F) annually, with a classic Mediterranean climate — hot dry summers and mild wet winters.
What Does the Temperature Feel Like in San Marcos?
Temperature alone doesn't tell the whole story — humidity plays a big role in how warm or cold it actually feels. High humidity in summer makes the heat feel more intense, particularly once temperatures climb above 25°C. In winter, the same humidity can make cold air feel sharper than the thermometer suggests.
In San Marcos, January is the coolest month, with average highs of 17°C (63°F) and humidity around 67% — considered high. In August, the warmest month, temperatures average 37°C (99°F) with 64% humidity — conditions that feel high. For a full picture, see our humidity page.
Climate temperature data is typically calculated as a 30-year average. This smooths out year-to-year variability and gives a more reliable picture of what a place is actually like, rather than what happened in any single unusual year.
The readings come from a range of sources — land-based weather stations, ocean buoys, ships, and satellites. That data is collected by weather services around the world, then pooled, quality-checked, and averaged to produce the climate records you see here.
For cities and regions with significant elevation, altitude is one of the biggest factors shaping local temperatures. As a rule of thumb, temperatures fall by around 6°C for every 1,000 metres gained — so a city at 2,000 metres will typically be around 12°C cooler than a city at sea level in the same region. Higher ground also tends to see more dramatic day-to-night temperature swings, since thinner air loses heat faster after sunset.
For more on San Marcos's weather — including monthly rainfall, sunshine hours, and humidity — visit our San Marcos climate page.
