30-year climate normals

San Luis Obispo County Climate and Weather Averages

Hottest month — September

79.5°

average daily high. The coldest month is December, averaging a low of 40.2°F.

San Luis Obispo County gets 17.94" of precipitation a year, and 59% of it falls in Dec, Jan, Feb.

Temperature through the year

Each bar spans the average daily low to the average daily high for that month.

Month	Avg high	Avg low	Precip
January	65.0°	40.6°	3.86"
February	65.1°	42.4°	3.54"
March	66.7°	44.5°	3.17"
April	69.1°	45.6°	1.05"
May	72.0°	47.8°	0.47"
June	75.2°	51.1°	0.10"
July	78.0°	54.3°	0.08"
August	79.3°	54.9°	0.01"
September	79.5°	53.4°	0.04"
October	77.2°	49.7°	0.92"
November	71.1°	44.7°	1.43"
December	64.9°	40.2°	3.27"

Rainfall by month

San Luis Obispo County has a distinct wet season. 59% of the year's precipitation arrives in Dec, Jan, Feb.

January 3.86"

February 3.54"

March 3.17"

April 1.05"

May 0.47"

June 0.10"

July 0.08"

August 0.01"

September 0.04"

October 0.92"

November 1.43"

December 3.27"

Annual total 17.94"

What this climate costs you

Degree days measure how hard a building has to work to stay comfortable. They are the reason two identical houses have very different power bills, and they are the link between the weather here and what you pay every month.

Cooling degree days How much air conditioning the climate demands 334

Heating degree days How much heating the climate demands 2,265

Approximate annual cooling cost At 33.25¢/kWh, California average $111

Approximate annual electric heating cost Lower where heating is gas rather than electric $264

These are rough planning figures from degree days and the state electricity price, not a bill estimate. House size, insulation and fuel type move them a lot. See the full cost of owning a home in San Luis Obispo County, where electricity is one line of eight.

Common questions

What is the weather like in San Luis Obispo County?

San Luis Obispo County averages a high of 79.5°F in September and a low of 40.2°F in December. Annual precipitation is 17.94 inches, with essentially no snow.

When is the rainy season in San Luis Obispo County?

The wettest stretch is Dec, Jan, Feb, which accounts for 59% of the year's precipitation. That is a pronounced wet season rather than rain spread evenly through the year.

How hot does it get in San Luis Obispo County?

The average daily high in September, the hottest month, is 79.5°F. That drives 334 cooling degree days a year, which is what your air conditioning has to work against.

Does it snow in San Luis Obispo County?

Effectively no. Measurable snowfall is rare in San Luis Obispo County.

Sources

Temperature, precipitation and snowfall normals — NOAA National Centers for Environmental Information, 1991–2020 Monthly Climate Normals, station SAN LUIS OBISPO AP, CA US (USW00093206), 15.1 miles from the county centroid.
Heating and cooling degree days — NOAA, same station and period.
Electricity price — US Energy Information Administration, Electric Power Monthly Table 5.6.A, California residential average.
Wet-season share is the wettest three consecutive months as a percentage of annual precipitation, calculated from the monthly normals.