San Marcos (CA) Temperature by Month
San Marcos in California, United States of America sees moderate seasonal temperature shifts, with daytime highs between 19°C (66°F) in December and 30°C (86°F) in August, averaging 24°C (75°F) annually. Explore the full monthly breakdown below.
San Marcos Monthly Temperatures
San Marcos experiences balanced seasonal shifts, with noticeable but moderate temperature variations. At night, minimum temperatures range from 17°C (63°F) in August to 7°C (45°F) in December.
The chart below illustrates the average maximum day and minimum night temperatures in San Marcos by month:
Daily lows are most common between 4 AM and 6 AM. By 3 PM temperatures reach their daily high, driven by peak solar heating. August, the warmest month of the year, receives 295 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.
very warm
warm
pleasant
moderate
cold
very cold
San Marcos vs World: Temperature Compared
San Marcos's average annual maximum temperature is 24°C (75°F). To put that in context, here's how it compares to a few well-known destinations:
Barcelona, Spain has an annual average of around 21°C (70°F), with warm summers and mild, fairly short winters.
Queenstown, New Zealand averages 10°C (50°F) annually — remember seasons are flipped, so its coldest months fall in June and July.
Chicago, USA averages 15°C (59°F) annually — known for extreme seasonal swings, from bitterly cold winters to warm summers.
Tokyo, Japan averages 21°C (70°F) a year, with hot summers, cool winters, and a well-defined cherry blossom spring.
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, December is the coolest month, with average highs of 19°C (66°F) and humidity around 64% — considered high. In August, the warmest month, temperatures average 30°C (86°F) with 74% 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.
Whether a city sits on the coast or deep inland makes a significant difference to its climate. Coastal areas tend to have more stable temperatures year-round — large bodies of water absorb heat slowly in summer and release it gradually in winter, keeping extremes in check. Cities far from the sea don't benefit from that buffer, which is why continental climates tend to have hotter summers and colder winters than their coastal counterparts at the same latitude.
For more on San Marcos's weather — including monthly rainfall, sunshine hours, and humidity — visit our San Marcos climate page.
