Average Weather In September For South Lake Tahoe, California, USA

Location

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%).

Temperature

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.

Daily High and Low Temperature in September

The daily average low (blue) and high (red) temperature with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).
Daily low temperatures range from 35°F to 42°F, falling below 28°F or exceeding 52°F only one day in ten.

Fraction of Time Spent in Various Temperature Bands in September

The average fraction of time spent in various temperature bands: frigid (below 15°F), freezing (15°F to 32°F), cold (32°F to 50°F), cool (50°F to 65°F), comfortable (65°F to 75°F), warm (75°F to 85°F), hot (85°F to 100°F) and sweltering (above 100°F).

Sun

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.

Daily Hours of Daylight and Twilight in September

The number of hours during which the Sun is visible (black line), with various degrees of daylight, twilight, and night, indicated by the color bands. From bottom (most yellow) to top (most gray): full daylight, solar twilight (Sun is visible but less than 6° from the horizon), civil twilight (Sun is not visible but is less than 6° below the horizon), nautical twilight (Sun is between 6° and 12° below the horizon), astronomical twilight (Sun is between 12° and 18° below the horizon), and full night.

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.

Daily Sunrise & Sunset with Twilight and Daylight Savings Time in September

The solar day over the course of the year 2012 . From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (solar, civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray. The transitions to and from daylight savings time are indicated by the "DST" labels.

Clouds

The median cloud cover is 5% (clear) and does not vary substantially over the course of the month.

Median Cloud Cover in September

The median daily cloud cover (black line) with percentile bands (inner band from 40th to 60th percentile, outer band from 25th to 75th percentile).

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.

Cloud Cover Types in September

The fraction of time spent in each of the five sky cover categories. From top (most blue) to bottom (most gray), the categories are clear, mostly clear, partly cloudy, mostly cloudy, and overcast. Pink indicates missing data. Outside of the United States clear skies are often reported ambiguously, leading them to be lumped in with the missing data.

Precipitation

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.

Probability of Precipitation at Some Point in the Day in September

The fraction of days in which various types of precipitation are observed. If more than one type of precipitation is reported in a given day, the more severe precipitation is counted. For example, if light rain is observed in the same day as a thunderstorm, that day counts towards the thunderstorm totals. The order of severity is from the top down in this graph, with the most severe at the bottom.

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.

Types of Precipitation Throughout September

Relative frequency of various types of precipitation over the course of a typical September.

Snow

The likelihood of snow falling is highest around September 30, occurring in 4% of days.

Probability of Snow Fall Being Reported in a Given Day in September

Probability that snow will be reported at least once in a given day.

Either snow rarely accumulates at this location in September or snow depth measurements are unavailable or unreliable.

Humidity

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.

Relative Humidity in September

The average daily high (blue) and low (brown) relative humidity with percentile bands (inner bands from 25th to 75th percentile, outer bands from 10th to 90th percentile).

Dew Point

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).

Dew Point in September

The daily average low (blue) and high (red) dew point with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).

Wind

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).

Wind Speed in September

The average daily minimum (red), maximum (green), and average (black) wind speed with percentile bands (inner band from 25th to 75th percentile, outer band from 10th to 90th percentile).
The wind is most often out of the south (22% of the time). The wind is least often out of the east (1% of the time), west (1% of the time), north west (2% of the time), south east (2% of the time), and north east (3% of the time).

Wind Directions in September

The fraction of time spent with the wind blowing from the various directions over the entire year. Values do not sum to 100% because the wind direction is undefined when the wind speed is zero.

Fraction of Time Spent with Various Wind Directions in September

The fraction of time spent with the wind blowing from the various directions on a daily basis. Stacked values do not always sum to 100% because the wind direction is undefined when the wind speed is zero.