For the first two weeks of September, the average maximum temperature in downtown San Francisco was 77.8 degrees Fahrenheit, making it the fifth-hottest start to the month since 1921.

Data from the oldest downtown meteorological station recorded the highest temperatures five years ago, when the average maximum temp hit 82.7 degrees between Sept. 1 and Sept. 11. The city’s hottest day ever was Sept. 1, 2017, when the maximum temperature reached 106 degrees.

The three other hot starts to September occurred in 1983, 1984, and 2004. 

What does this mean in terms of climate change?

2022 has the fifth hottest start of September since 1921.

Meteorologist said we’re experiencing more fluctuating and warmer temperature since 1980s.

82.7

82

79.5

78.7

80

77.8

2022 average

5-year

average

highest

temperature

75

70

65

every year

average

highest

temperature

60

2020

1920

1945

1970

1995

Note: the time period shown above is between Sept. 1 to Sept. 11

2022 has the fifth hottest start of September since 1921.

Meteorologist said we’re experiencing more fluctuating and warmer temperature since 1980s.

5-year

average

highest

temperature

every year

average

highest

temperature

2022 average

77.8°F

1920

1945

1970

78.7

1983

1984

82

1995

79.5

2004

82.7

2017

2020

Note: the time period shown above is between Sept. 1 to Sept. 11

“The patterns for the more recent years, since the mid-1980s, seem to be warmer and, especially, more fluctuating,” said Charles Fisk, a member of the American Meteorological Society.

Compared to the years before 1980, the average temperature has increased by 2 degrees Fahrenheit. Meteorologists said this is consistent with how they would expect the climate to behave in the 21st century.

John P. Monteverdi, professor emeritus of meteorology at San Francisco State University, said the heat can likely be attributed to global warming, but scientists prefer to wait for all the data to see if there are any extenuating circumstances.

As long as the extreme heat continues, power outages will follow. Exactly that happened last week.

On Tuesday, Sept. 6, the hottest day of the latest heat spell at 98 degrees Fahrenheit,  Pacific Gas and Electric provided a record-breaking 22,684 MW of power to its customers, 50 percent more than it would normally provide. The outage that day affected more than 210,000 people.

At around 3 p.m. last Thursday, the soaring temperatures also brought on a power outage in nearly a straight line from Dogpatch through to Noe Valley. Approximately 5,800 Pacific Gas & Electric customers lost power.

More than 95 percent of the utility’s customers got their power back in an hour, as PG&E dispatched crews to Shotwell Street and 20th Street for repairs while the distribution control center connected customers to other power sources. The remaining customers, who were served directly by the damaged equipment, had their power restored at 6:54 p.m.

Stress on the equipment, said Mayra Tostado, a PG&E spokesperson, explained the outage.

Two hottest days last week were when most outage happened, according to PG&E.

PG&E provided record-breaking 22,684 MW of power to customers last Tuesday, Sept. 6.

.

On Tuesday, the outages

affected 217,505 customers.

98°F

95

On Thursday, the outages

affected 11,085 customers,

including 5,800 in Mission.

90

87°F

85

80

75

70

max temp

65

64°F

62°F

60

min temp

55

09/01

09/02

09/03

09/04

09/05

09/06

09/07

09/08

09/09

09/10

09/11

Two hottest days last week were when most outage happened, according to PG&E.

PG&E provided record-breaking 22,684 MW of power to customers last Tuesday, Sept. 6.

217,505 customers

affected by outage

11,085 customers

affected, including

5,800 in Mission

98°F

95

87°F

max temp

64°F

62°F

55

min temp

09/01

09/06

09/08

09/11

“What was extreme in the 20th-century climate is less extreme now, in the new climate mode,” said Monteverdi.

“In other words, people would say, ‘Oh, that was a really hot day.’ But it’s going to be more typical.”

Wider swings from the average are also expected in the Bay Area, not only in temperature, but also in rainfall. This means there will be more droughts and cold snaps as well, said Monteverdi. However, although climate change is certainly a driver of unusual weather events, it is difficult to attribute every event directly to global warming until more data is collected, he said.

The Bay Area has always experienced a cool summer and its warmer weather in September, and that is still the case. But the difference is that the autumn heat is now liable to be more extreme. The data shows that the highest temperature every month in recent years is higher, compared to years before the 1980s.

Bay Area has always experienced a cool summer and its warmer weather in September.

But data shows the higest temperature every month in recent years is slightly higher than 40 years ago.

105

100

95

90

post-1980 highest

temp per month

85

80

75

70

65

60

pro-1980 highest

temp per month

55

Jan

Feb

Mar

Apr

May

Jun

Jul

Sep

Oct

Nov

Dec

Aug

Bay Area has always

experienced a cool summer and its warmer weather in September

But data shows the higest temperature every month in recent years is slightly higher than 40 years ago

pro-1980 highest

temp per month

post-1980 highest

temp per month

cooler

hotter

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Note: Data analysis process can be found here.

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INTERN DATA REPORTER. Chuqin has two degrees in data journalism and she is passionate about making data more accessible to readers. Before arriving in the Mission, she covered small business and migratory birds in New York City while learning to code and design at Columbia's Graduate School of Journalism. She loves coastal cities, including SF and her hometown Ningbo.

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  1. Indian summers follow a frost. Perhaps Mission Local (or the loyal readers) can coin an appropriate term for what used to be two warm weeks in October but now are randomly occurring episodes of heat. I have experienced warm fog on the golden gate bridge as well, rather than the usual cold stuff. We need new names for the Global Weirding we are experiencing locally.

    1. Hi Janos, thanks for clarifying that. I consulted two meteorologists too and they told me the term doesn’t really apply to the west coast. So I’ve changed it in the article 🙂