September Weather in San Diego: Hottest on Record, Average Temperatures, and Humidity

San Diego, California, USA downtown city skyline.
© Sean Pavone/

Written by Patrick MacFarland

Updated: August 29, 2023

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Sunny San Diego. America’s Finest City. That’s just a few of the nicknames San Diego has. If you want to visit San Diego in September, you’re in for a great time. The weather will be perfect with almost zero chance of rain. You can hit one of the many beaches in San Diego — from Pacific Beach to Mission Beach — and soak in the sun. When you leave the city, you’ll want to stay and never leave. You will explore a lot of places and cherish a lot of memories. 

If you are considering going to San Diego in September or have already booked your trip, we’ll give you the low down on the average temperatures, temperature records, and humidity for the month. We’ll also take a look at some fun things to do and delicious things to eat while you are in San Diego.

Shelter Island, San Diego, Ca 92107

San Diego is nicknamed “America’s Finest City,” coined by then-mayor Pete Wilson after San Diego lost the bid on hosting the Republican National Convention.

©Ted Caplaneris/

Average Temperature in San Diego

San Diego in September is an amazing month. There hardly is rain and the sun shines brightly all day. If you visit America’s Finest City in September, you’ll be in luck. When it comes to the average temperature in September, it ranges from a high of 77 degrees Fahrenheit (25 degrees Celsius) to a low of 18 degrees Fahrenheit (24 degrees Celsius).

In terms of daylight hours, sunrise is around 6:30 a.m. and sunset is at around 7:00 p.m., which gives you almost 13 hours of daylight. That’s plenty of time to explore San Diego and its beautiful natural parks and hit the beach, too!

The Hottest Temperature on Record

September is a hot month in San Diego with very little rainfall, thus hotter temperatures are more common. When it comes to records, the hottest temperature in September ever recorded was 111 degrees Fahrenheit (44 degrees Celsius) on September 26, 1963.

San Diego on the map

The first Jack-in-the-Box in the nation was built in San Diego.


The Coldest Temperature on Record

September in San Diego is a hot and dry month. But sometimes, anomalies happen. The coldest temperature in September ever recorded was 50 degrees Fahrenheit (10 degrees Celsius) on September 26, 1907.

Rainfall in September

Rainfall is not common in San Diego during September. Less than half an inch of rain falls on San Diego in September. If you’re thinking of visiting the city this month, you should have no worries about potential rain. There is also no humidity, and the heat is quite dry.

UV Index in September

San Diego has near-perfect weather year-round. This means the sun will be shining brightly throughout the day. The sun’s ultraviolet rays can be damaging when the UV Index is high. For San Diego in September, there is a UV Index of 7. This means that sun exposure can cause damage to the skin and eyes fairly quickly.

To protect yourself, it is recommended you wear sunscreen. Continue to put on sunscreen throughout the day to make sure you don’t get sunburnt. Wear loose clothing to avoid overheating and get a hat to cover yourself, too.

Natural Disasters in September

Because of San Diego’s location, the city and county are extremely vulnerable to natural disasters. These include fires, earthquakes, and flooding due to extreme rain. Scientists have long declared that Californians should brace themselves for “the big one.” They are referring to the big earthquake that can damage the state.

Wildfires are also a real threat to San Diego. The biggest wildfire recorded in San Diego history was the Cedar Fire in October 2003, which destroyed thousands of homes, cost one billion dollars in damage, and killed 15 people. Impacts of the wildfires still affect San Diegans today.

In terms of natural disasters in September, not many have struck San Diego this month. As climate change continues ravaging the planet, San Diego is at risk for wildfires and earthquakes any time of the month.

Visiting San Diego in September

La Jolla

Dr. Seuss, the author of many children’s books that include

How the Grinch Stole Christmas

, lived in the La Jolla neighborhood of San Diego.


With amazing weather year-round, it’s really easy to visit San Diego and have a grand old time. Explore the Downtown area and its Victorian and early 20th-century architecture. If you want to learn about San Diego’s history, visit Old Town and even explore what buildings during the 1700s looked like. You can also have lunch there and go inside the trinket shops. 

A visit to San Diego wouldn’t be complete without going to Balboa Park and the San Diego Zoo. There are art museums, history museums, and even a train museum in Balboa Park. There is a theater called The Old Globe, which is fashioned like Shakespeare Globe Theater if you want to go see a play. And if you want some Zen time, there is also the Japanese Friendship Garden. If you want to continue your San Diego education, trek up to the Cabrillo National Monument where you can learn when the first Spanish settlers arrived at San Diego Bay. 

Finally, for those nature lovers out there, head north and hike the Torrey Pines State Preserve. Hiking trails in this park will ensure you get scenic views of the city and ocean.

Things to Eat and Drink in San Diego

San Diego is an eclectic mix of so many cultures. You can go to different neighborhoods in San Diego and see how everything changes — the restaurants, the vibe, the cultures. When it comes to food, San Diego is rich in the variety of what you should eat. 

First and foremost, try the California burrito. After all, San Diego is where the California burrito was invented. It’s a carne asada burrito with guacamole, sour cream, and french fries. It will be a taste explosion! If you drive up to Convoy Street in the Kearny Mesa neighborhood of San Diego, make sure you check delicious Korean and Chinese restaurants. You can order some Korean-style chicken wings.

Lastly, have a fancy Italian dinner at one of the many restaurants in Little Italy. Afterward, enjoy a beer at a local brewery. San Diego is home to hundreds of breweries.

Fun Facts About San Diego

Coronado California dawn. Dawn arrives at Coronado Island revealing the bay, golf course, village and coronado bridge.

The Coronado Bridge opened on August 3, 1969.


  • The first person to drive across the Coronado Bridge was Ronald Reagan, who was governor of California at the time.
  • The rarest pine tree in the world, the Torrey pine, is only found in two places: San Diego and Santa Rosa Island.
  • San Diego was the first permanent settlement by the Spanish.
  • The first California mission, San Diego de Alcalá, was founded on July 16, 1769.
  • There are more than 600 marine species found in San Diego’s waters, including sea urchins and sea stars.
  • One of the most visited zoos in the world is San Diego Zoo.
  • San Diego is the #1 producer of avocados in the United States.


San Diego is home to a diverse ecosystem with a range of climates that is unique for this part of the United States. Every hour you spend in San Diego will be filled with fun activities ranging from city exploration to nature hikes. You will learn about the rich history of San Diego but also enjoy the cultural parts of what makes San Diego a special place. 

With the border only 10 minutes away, make sure you have your passport ready to cross the Mexican border to explore Tijuana and see a whole new world. There’s a lot to see on both sides of the border to enhance your experience. When the vacation is over, you’ll wish you lived in San Diego!

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About the Author

Patrick Macfarland is a writer at A-Z Animals primarily covering travel, geography, and history. Patrick has been writing for more than 10 years. In the past, he has been a teacher and a political candidate. He holds a Bachelor's Degree in Political Science from SDSU and a Master's Degree in European Union Studies from CIFE. From San Diego, California, Patrick loves to travel and try new recipes to cook.

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