Palo Alto in September

Ask a local about the best weather of the year and many will say September. The summer fog on the coast thins out, the bay breeze softens and the days are reliably warm. It is also the month when Palo Alto changes gear. Schools are back, thousands of new Stanford students arrive and football Saturdays bring crowds to the stadium on El Camino Real. Business travel returns after the summer lull.

This guide covers the weather, the heat and fire season, what is in season and the events that fill the month. It also has the school and university dates that move hotel prices, plus packing tips, booking advice, day trips and a weekend plan. Dates are given only where organizers have published them. Otherwise we describe the usual timing and link to the source.

September weather in Palo Alto

These are NOAA's 1991 to 2020 climate normals for the Palo Alto station (USC00046646), the same data used on our weather page. Sun times are approximate, in Pacific Daylight Time.

September has the highest average high of the year, though only by a fraction of a degree. What sets it apart is the heat waves. A typical September brings close to four days at 90°F or more and the city's all-time record of 108°F was set on September 6, 2022. Nights cool down more than in July, with lows near 53°F, so the daily swing can be large. Rain is rare. When it does fall, it is usually a brief early storm late in the month.

Days shorten quickly. The sun sets about 45 minutes earlier at the end of the month than at the start. The National Weather Service Bay Area office posts heat advisories and Red Flag Warnings.

What is in season

Peak fire season

By September the grass in the foothills has been dry for months. Fire danger runs high into the fall, especially when warm, dry winds blow from the north and east. During Red Flag Warnings some trails in the hills close and Stanford can restrict access to the Dish. Check before you drive to a trailhead. Wildfire smoke from elsewhere in California can also affect the air here, so look at AirNow before strenuous plans. Residents can read our emergency preparedness guide for wildfire and earthquake planning.

Birds and the bay

Shorebird numbers keep building at the Baylands through September and the first wintering ducks begin to arrive late in the month. The wind is usually lighter than in midsummer, which makes the levees pleasant for walking and birding later in the day.

Farmers market produce

September is the crossover month. Tomatoes, peppers, melons and figs are still plentiful, while grapes, apples, pears and the first pomegranates arrive. Both city markets run every weekend of the year: downtown on Saturday mornings and California Avenue on Sunday mornings.

September events

Stanford football

Home games bring tens of thousands of fans to Stanford Stadium. In 2026 September home games included a Friday night game against Miami on September 4 and Georgia Tech on September 26. Stanford's 2027 schedule had not been released in October 2026. The ACC has named the 2027 conference home opponents as Cal, Duke, North Carolina, Syracuse and Virginia, so watch gostanford.com for dates. Tickets are sold through Stanford Athletics, not Ticketmaster. Kickoff times are sometimes set only a week or two ahead.

Use Caltrain to Palo Alto station on game days. Caltrain's Stanford station did not open for 2026 games. Our athletics guide covers tickets, bags and tailgating.

Moonlight Run and Walk

The Palo Alto Weekly Moonlight Run and Walk is a local fall tradition: a nighttime 5K and 10K along the bay. The 42nd edition was on Friday, September 25, 2026, starting from the Baylands Athletic Center at 1900 Geng Road, with the 5K walk at 7 p.m. and the timed runs after 8 p.m. The organizers left out the half marathon in 2026 because of construction on the route. Watch the race's registration page for the next date.

Thursday Live

The city's free evening street parties on the car-free block of California Avenue run from May through September, on one Thursday each month from 5 to 8 p.m. September is the last chance of the year. Check the city calendar for the date.

Holidays and school calendars

Labor Day opens the month. It fell on Monday, September 7, in 2026. In 2027 it falls on Monday, September 6. Palo Alto Unified schools are closed that day. Many Bay Area families take a last summer trip that weekend, so roads to the coast and Lake Tahoe are busy.

Stanford's year starts in earnest in mid-September. According to Stanford's academic calendar for new students, move-in was Tuesday, September 15, 2026. Autumn quarter classes began a week later, on Tuesday, September 22. Expect a week of orientation, families on campus and full hotels nearby. The 2027 move-in date had not been published in October 2026, but mid-September is the usual pattern.

The PAUSD school year is in full swing by September, so weekday traffic near schools is heavy at drop-off and pickup times. The district's calendar page lists all closures.

What to pack

• Hot weather clothes for the afternoon, in case a heat wave hits.
• A sweater for cool evenings and night football games.
• A clear bag if you are going to a game. Stanford enforces a clear bag policy at the stadium.
• A hat and plenty of water for any hike.
• Swimwear and a light jacket for the coast, which is often at its sunniest this month.

Hotel demand and booking tips

September is one of the busiest hotel months of the year in Palo Alto. Move-in week brings thousands of families at once. Home football weekends fill rooms near campus. Business travelers return after Labor Day and fall conferences in Silicon Valley take up weekday rooms across the Peninsula.

• Book move-in week and game weekends as soon as you know your dates. Our guide to staying near Stanford lists hotels within reach of campus.
• Weekday rates at business hotels can be high. A Friday or Saturday night is sometimes cheaper unless there is a home game.
• If Palo Alto is full, look along the Caltrain line in Menlo Park, Mountain View or Redwood City.

You can compare hotels for your September dates and choose a refundable rate while plans settle.

Outdoor activities for September

1. Hike at dawn. The Stanford Dish loop is busiest and hottest at midday. Early morning is cooler and the light is better.
2. Bike the bay in the evening. Lighter winds make late-day rides along the Baylands levees pleasant.
3. End the day at the bay. Sunset at the Baylands comes before 7:40 p.m. all month, early enough for an after-work walk on the levees.
4. Watch a game on campus. Besides football, fall brings women's volleyball and soccer to Stanford. Check gostanford.com for free and ticketed events.
5. Skip the heat. On a 95°F day, spend the afternoon in an air-conditioned museum and save the trail for the next morning.

Day trips that suit September

• The coast. September often brings the clearest, warmest beach days of the year to Half Moon Bay and the San Mateo coast. Highway 92 can back up on sunny weekends, so leave early.
• Wine country at harvest. Grapes come in from late summer through October in Napa and Sonoma. It is the liveliest and busiest time to visit and many wineries require reservations. A guided tour saves the drive back. You can book a Napa or Sonoma wine tour.
• Santa Cruz or Monterey. Both get some of their best weather now, with fewer summer crowds after Labor Day.

If you only have a weekend

1. Saturday at dawn: hike the Dish before the heat.
2. Saturday morning: the downtown farmers market, then breakfast nearby.
3. Saturday afternoon: a home football game if one is scheduled. If not, walk the Main Quad and the Rodin Sculpture Garden.
4. Saturday evening: dinner downtown or on California Avenue. Book ahead on game nights.
5. Sunday: drive to Half Moon Bay for a beach walk in the sun, back by evening.

For the start of fall color and the first rains, read Palo Alto in October. Late summer is covered in Palo Alto in August.

Frequently asked questions