This report describes the typical weather at the Lake Tahoe Airport (South Lake Tahoe, California, United States) weather station over the course of an average September. It is based on the historical records from 1974 to 2012. Earlier records are either unavailable or unreliable.
South Lake Tahoe, California has a continental climate with dry warm summers. The area within 25 mi of this station is covered by forests (62%), shrublands (15%), grasslands (11%), and lakes and rivers (10%).
The month of September is characterized by falling daily high temperatures, with daily highs decreasing from 76°F to 68°F over the course of the month, exceeding 83°F or dropping below 57°F only one day in ten.
Over the course of September, the length of the day is decreasing. From the start to the end of the month, the length of the day decreases by 1:12 hours, implying an average day-over-day decrease of 2.4 minutes.
The shortest day of the month is September 30 with 11:48 hours of daylight; the longest day is September 1 with 13:00 hours of daylight.
The earliest sunrise is at 6:29am on September 1; the latest sunset is at 7:29pm on September 1; the latest sunrise is at 6:55am on September 30; the earliest sunset is at 6:43pm on September 30.
Daylight savings time is observed in 2012 but it neither starts nor ends in September, so the entire month is in daylight time.
The median cloud cover is 5% (clear) and does not vary substantially over the course of the month.
On September 15, a representative day, the sky is clear or mostly clear 49% of the time, partly cloudy 8% of the time, and mostly cloudy or overcast 13% of the time.
The average probability that some form of precipitation will be observed in a given day is 14%, with little variation over the course of the month.
Throughout September, the most common forms of precipitation are thunderstorms, light rain, and light snow.
Thunderstorms are the most severe precipitation observed during 38% of those days with precipitation. They are most likely around September 1, when it is observed during 7% of all days.
Light rain is the most severe precipitation observed during 34% of those days with precipitation. It is most likely around September 30, when it is observed during 6% of all days.
Light snow is the most severe precipitation observed during 10% of those days with precipitation. It is most likely around September 30, when it is observed during 3% of all days.
The likelihood of snow falling is highest around September 30, occurring in 4% of days.
Either snow rarely accumulates at this location in September or snow depth measurements are unavailable or unreliable.
The relative humidity typically ranges from 26% (dry) to 89% (very humid) over the course of a typical September, rarely dropping below 14% (very dry) and reaching as high as 100% (very humid).
The air is driest around September 3, at which time the relative humidity drops below 29% (dry) three days out of four; it is most humid around September 27, rising above 82% (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 typical September, the dew point typically varies from 27°F (dry) to 43°F (dry) and is rarely below 18°F (dry) or above 52°F (very comfortable).
Over the course of September typical wind speeds vary from 0 mph to 13 mph (calm to moderate breeze), rarely exceeding 18 mph (fresh breeze).
The highest average wind speed of 5 mph (light breeze) occurs around September 1, at which time the average daily maximum wind speed is 13 mph (moderate breeze).
The lowest average wind speed of 5 mph (light breeze) occurs around September 30, at which time the average daily maximum wind speed is 12 mph (gentle breeze).