Monthly climate in San Marcos, California, United States

Last updated: March 2, 2024

Under the Köppen–Geiger climate classification San Marcos features a hot-summer Mediterranean climate (Csa). Temperatures typically range between 13 °C (56 °F) and 24 °C (75 °F) through the year, but rarely can drop to 3 °C (37 °F) or can rise to as high as 40 °C (105 °F). The average annual precipitation amounts to about 402 mm (15.8 inches) and receives 40 rainy days on the 1 mm (0.04 inches) threshold annually. San Marcos enjoys an average of 3627 hours of sunshine throughout the year, and daylight varies from 9 hours 59 minutes to 14 hours 17 minutes per day.

Monthly average temperatures in San Marcos, California, United States §

The warmest months in San Marcos are July, August and September, with daily mean temperatures ranging from 23 to 24 °C (73 - 75 °F) throughout the day. The coldest temperatures usually occur in January, February and December, when daily mean temperatures range from 13 to 14 °C (56 - 57 °F) throughout the day. On average each year, San Marcos experiences 110 days above 25 °C (77.0 °F) and 0 days below 0 °C (32.0 °F).

Monthly average temperatures with daily means, minimums and maximums for period, average high and low temperatures in San Marcos, California, United States. Generated using Copernicus Climate Change Service information. Data for period from January 2017 to June 2022.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Maximum 30°C
(87°F)
29°C
(85°F)
28°C
(83°F)
34°C
(93°F)
30°C
(87°F)
33°C
(92°F)
40°C
(105°F)
34°C
(94°F)
40°C
(104°F)
39°C
(103°F)
33°C
(92°F)
28°C
(83°F)
Mean maximum 27°C
(81°F)
25°C
(77°F)
26°C
(79°F)
30°C
(86°F)
29°C
(84°F)
30°C
(86°F)
33°C
(92°F)
33°C
(92°F)
35°C
(95°F)
35°C
(95°F)
32°C
(90°F)
25°C
(77°F)
Average high 19°C
(66°F)
18°C
(65°F)
19°C
(66°F)
21°C
(70°F)
21°C
(71°F)
24°C
(76°F)
28°C
(82°F)
29°C
(84°F)
28°C
(82°F)
26°C
(79°F)
23°C
(73°F)
19°C
(66°F)
Daily mean 13°C
(56°F)
13°C
(56°F)
14°C
(58°F)
16°C
(62°F)
17°C
(63°F)
20°C
(68°F)
23°C
(73°F)
24°C
(75°F)
23°C
(73°F)
20°C
(69°F)
17°C
(63°F)
14°C
(57°F)
Average low 9°C
(48°F)
9°C
(48°F)
10°C
(50°F)
12°C
(54°F)
14°C
(57°F)
16°C
(61°F)
19°C
(67°F)
20°C
(68°F)
19°C
(66°F)
15°C
(60°F)
12°C
(54°F)
9°C
(49°F)
Mean minimum 5°C
(42°F)
4°C
(39°F)
6°C
(43°F)
9°C
(48°F)
10°C
(51°F)
13°C
(56°F)
16°C
(61°F)
17°C
(63°F)
16°C
(60°F)
11°C
(52°F)
8°C
(47°F)
4°C
(40°F)
Minimum 4°C
(40°F)
3°C
(37°F)
5°C
(41°F)
8°C
(46°F)
9°C
(49°F)
12°C
(54°F)
15°C
(60°F)
16°C
(62°F)
13°C
(55°F)
8°C
(47°F)
7°C
(45°F)
3°C
(39°F)

Compare climate in San Marcos with other places

Compare temperature, precipitation, sunshine, UV index in San Marcos, California, United States with other places around the world.

Monthly average precipitation in San Marcos, California, United States §

San Marcos usually has the most precipitation in January, February and December, with an average of 5 rainy days and 73 mm (2.9 inches) of precipitation per month. The driest months in San Marcos are June, July and August. On average, 3 mm (0.1 inches) of precipitation falls during these months.

Monthly average precipitation and precipitation days in San Marcos, California, United States. Generated using Copernicus Climate Change Service information. Data for period from January 2017 to January 2022.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Average precipitation mm (inches) 70 (2.8) 78 (3.1) 68 (2.7) 32 (1.3) 24 (0.9) 3 (0.1) 4 (0.2) 1 (0.1) 5 (0.2) 12 (0.5) 34 (1.4) 70 (2.7)
Average precipitation days (≥ 1 mm) 5 6 10 3 4 0 0 0 1 2 3 6

Monthly sunshine hours in San Marcos, California, United States §

The sunniest months in San Marcos are May, June and July, when the sun shines an average of 12 hours 4 minutes a day. Least sunny months in San Marcos: January, February and December receive an average of 7 hours 16 minutes of sunshine daily.

Mean monthly sunshine duration, average sunshine hours per day and mean daily daylight hours in San Marcos, California, United States. Generated using Copernicus Atmosphere Monitoring Service information. Data for period from January 2017 to January 2022.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Mean monthly sunshine hours 191 242 298 324 363 368 377 361 318 296 256 227
Mean daily daylight hours 10h 13m 11h 0m 12h 0m 13h 1m 13h 52m 14h 17m 14h 3m 13h 18m 12h 19m 11h 18m 10h 25m 9h 59m

Solar UV radiation in San Marcos, California, United States §

San Marcos experiences the highest level of ultraviolet (UV) radiation in May, June and July, when the maximum UV index can reach values of 11 - 12, which corresponds to the Extreme category of sun exposure. January, November and December are in the Moderate exposure category. In these months, the maximum values of the UV index do not exceed 5. For more detailed information, check out our hourly San Marcos UV Index data.

Average daily maximum UV levels by month for San Marcos, California, United States. Generated using Copernicus Atmosphere Monitoring Service information. Data for period from January 2022 to January 2023.
  Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
UV Index (month maximum) 4 6 9 10 11 12 11 10 10 7 5 4

Detailed Monthly Weather Insights for San Marcos, California, United States

Discover in-depth weather details for every month in San Marcos. Click through the links below for comprehensive overviews of temperature trends, precipitation levels, sunshine hours, and solar UV radiation specifics. Whether planning a visit or simply curious about San Marcos's climate nuances, these monthly breakdowns provide the information you need for an informed understanding of what to expect throughout the year.

Each link leads to a detailed account of the typical weather conditions for that month, providing both locals and tourists with vital information to plan their daily activities, wardrobe, and travel itineraries accordingly.