Over the course of a year, the temperature typically varies from 39°F to 97°F and is rarely below 29°F or above 101°F.
The warm season lasts from May 26 to September 16 with an average daily high temperature above 90°F. The hottest day of the year is August 11, with an average high of 97°F and low of 74°F.
The cold season lasts from November 24 to February 23 with an average daily high temperature below 69°F. The coldest day of the year is January 1, with an average low of 39°F and high of 63°F.
The length of the day varies significantly over the course of the year. The shortest day is December 21 with 10:13 hours of daylight; the longest day is June 20 with 14:04 hours of daylight.
The earliest sunrise is at 6:30am on June 13 and the latest sunset is at 8:37pm on June 28. The latest sunrise is at 7:47am on November 3 and the earliest sunset is at 5:31pm on December 3.
Daylight saving time (DST) is observed in this location during 2012, starting in the spring on March 11 and ending in the fall on November 4.
The median cloud cover ranges from 15% (mostly clear) to 51% (partly cloudy). The sky is cloudiest on April 6 and clearest on September 1. The clearer part of the year begins around June 27. The cloudier part of the year begins around October 30.
On September 1, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 74% of the time, and overcast or mostly cloudy 23% of the time.
On April 6, the cloudiest day of the year, the sky is overcast, mostly cloudy, or partly cloudy 49% of the time, and clear or mostly clear 45% of the time.
The probability that precipitation will be observed at this location varies throughout the year. Precipitation is most likely around July 17, occurring in 20% of days. Precipitation is least likely around January 15, occurring in 5% of days.
Over the entire year, the most common forms of precipitation are thunderstorms. Thunderstorms are the most severe precipitation observed during 98% of those days with precipitation. They are most likely around July 17, when it is observed during 20% of all days.
During the warm season, which lasts from May 26 to September 16, there is a 17% average chance that precipitation will be observed at some point during a given day. When precipitation does occur it is most often in the form of thunderstorms (100% of days with precipitation have at worst thunderstorms).
During the cold season, which lasts from November 24 to February 23, there is a 6% average chance that precipitation will be observed at some point during a given day. When precipitation does occur it is most often in the form of thunderstorms (91% of days with precipitation have at worst thunderstorms).
Snow is exceptionally unlikely to fall at any time during the year.
The relative humidity typically ranges from 37% (comfortable) to 89% (very humid) over the course of the year, rarely dropping below 21% (dry) and reaching as high as 98% (very humid).
The air is driest around August 10, at which time the relative humidity drops below 42% (comfortable) three days out of four; it is most humid around July 10, exceeding 85% (very humid) three days out of four.
Dew point is often a better measure of how comfortable a person will find the weather than relative humidity because it more directly relates to whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid.
Over the course of a year, the dew point typically varies from 28°F (dry) to 73°F (very muggy) and is rarely below 13°F (dry) or above 75°F (very muggy).
There are two periods in the year that are most comfortable: The first is between February 23 and May 2 and the second is between September 30 and November 26. The air feels neither too dry nor too muggy during these periods.
Over the course of the year typical wind speeds vary from 0 mph to 20 mph (calm to fresh breeze), rarely exceeding 25 mph (strong breeze).
The highest average wind speed of 11 mph (gentle breeze) occurs around March 29, at which time the average daily maximum wind speed is 19 mph (fresh breeze).
The lowest average wind speed of 7 mph (light breeze) occurs around September 10, at which time the average daily maximum wind speed is 14 mph (moderate breeze).
The wind is most often out of the south (28% of the time), north (16% of the time), and south east (12% of the time). The wind is least often out of the west (3% of the time).
The risk of tornado damage in San Marcos is lower than Texas average and is higher than the national average. The tornado index value is calculated based on historical tornado events data using USA.com algorithms. It is an indicator of the tornado level in a region. A higher tornado index value means a higher chance of tornado events. The tornado index for San Marcos ids 170.75, as compared to Texas which is 208.58, and the U.S. which is 136.45.
The chance of earthquake damage in San Marcos is about the same as Texas average and is much lower than the national average. The earthquake index value is calculated based on historical earthquake events data using USA.com algorithms. It is an indicator of the earthquake level in a region. A higher earthquake index value means a higher chance of an earthquake. The earthquake index for San Marcos ids 0.01, as compared to Texas which is 0.04, and the U.S. which is 1.81.
Source: weatherspark.com, July 2012. usa.com, July 2012.