Palo Alto weather in July

If you want guaranteed sunshine in Palo Alto, come in July. The month averages no rain at all. Most afternoons land between the mid 70s and mid 80s. Nights cool into the 50s. A gray marine layer drifts in on some mornings and clears before lunch. The weather is so steady that the most useful planning question is not whether it will be nice, but how cold it will be if you go to San Francisco.

These figures are NOAA's 1991 to 2020 climate normals for the Palo Alto station (USC00046646), located on the flats at about 25 feet. NOAA labels the station's values "representative" rather than "standard" because the record has gaps, so read small differences loosely. Sunrise and sunset times are calculated for central Palo Alto for July 2027 and agree with published tables within a minute. These are averages, not a forecast. Our weather guide compares every month.

July by the numbers

NOAA publishes no long term Half Moon Bay sea temperature. The ocean figure is its average for the buoy about 18 nautical miles west of San Francisco.

Warm, dry and steady

July's normal rainfall is 0.00 inches and its average count of rainy days rounds to zero. The only moisture most years is drizzle from a deep marine layer on a few mornings, which can dampen sidewalks near the bay without registering as real rain.

The Palo Alto station averages 12.6 days at 80°F or hotter in July. Only about 1.9 days reach 90°F, fewer than June's 2.8 or September's 3.7. That surprises people. July is consistently warm rather than extreme, because the marine layer is at its deepest and keeps the region air-conditioned from the west. A 100°F day averages about 0.2 times in July, or once every five years or so.

The daily swing is wide. Average lows of 55.7°F and highs of 79.4°F mean a cool morning and a warm afternoon on the same day. Restaurants with patios keep heaters for a reason.

Daylight

Days are still long but shrinking. Sunrise moves from about 5:51 a.m. on July 1 to about 6:12 a.m. on July 31. Sunset moves from about 8:33 p.m. to about 8:17 p.m. Daylight drops from about 14 hours 42 minutes to 14 hours 5 minutes, a change you will barely notice day to day.

Evenings are made for being outside. Stanford posts summer hours of 6 a.m. to 7:30 p.m. for the Dish. The Baylands is open until sunset. Midpen preserves stay open until half an hour after sunset.

Fog, smoke and air quality

Peak fog season, somewhere else

July and August are the heart of the Bay Area fog season. Strong northwest winds along the coast drive upwelling of cold water. Warm air over that water condenses into a deep marine layer. The sea breeze then pulls it inland through the Golden Gate, the San Bruno Gap and other low points in the coastal hills.

Palo Alto sits behind the Santa Cruz Mountains, which top 2,000 feet along Skyline Boulevard. Most days the fog stops at the ridge. When it is deep, it spills over in the evening and can bring a gray morning to the Peninsula. In Palo Alto it usually burns off by 10 or 11 a.m.

Smoke and ozone

Wildfire smoke can reach Palo Alto in July when large fires burn elsewhere in Northern California and winds carry the smoke our way. The worst recent smoke episodes have tended to come later, in August through November, but July is part of the season. Hot afternoons also raise ozone. The Air District can call summer Spare the Air alerts. Check AirNow and its Fire and Smoke Map on hazy days.

Fire danger in the hills is high by July. Fireworks of every kind are illegal in Palo Alto. Grass fires near roads and trails can start from a single spark.

Microclimates: bay, town, hills and ridge

On a warm July day, a half hour drive can change the temperature by 20 degrees or more. Moffett Field, on the bay in Mountain View, averages a July high of 76.9°F, about two and a half degrees cooler than the Palo Alto station, with warmer nights at 58.5°F. San Jose, farther from the bay breeze, averages 80.8°F.

Within Palo Alto, the Baylands catch a stiff afternoon wind off the water and stay cooler. Downtown and Midtown sit in the middle. The Stanford campus and the foothills warm most at midday. Exposed trails at Pearson-Arastradero and the Dish can be hot by noon.

West of the ridge everything changes. The coast side of the Santa Cruz Mountains stays cool and foggy. Redwood canyons drip with fog moisture all summer. A hike in a redwood park can feel much cooler than a Palo Alto sidewalk on the same afternoon.

How July compares with San Francisco and San Jose

July has the biggest gap of the year between Palo Alto and San Francisco. Downtown San Francisco averages a high of 66.3°F, cooler than its September or October average and actually a touch below its June figure. Palo Alto averages 79.4°F, about 13 degrees warmer. Western neighborhoods of the city near the ocean run cooler still.

San Jose is the warm end of the comparison, averaging 80.8°F with nights in the upper 50s. If you are planning a city day, bring a real jacket and a hat. If you would rather someone else handle the logistics, you can book a San Francisco tour and leave the car behind. Our San Francisco guide has more.

The coast in July

Ocean water warms slowly through summer. NOAA's buoy west of San Francisco averages 55.6°F in July and the Monterey buoy 56.9°F. NOAA does not publish a Half Moon Bay figure. The coast there is often foggy and in the 60s, with brief clear spells in the afternoon. Inside the bay, the Redwood City reading averages 71.9°F, about 16 degrees warmer than the open ocean.

That contrast is why locals paddle on the bay and walk on the coast. If you do swim in the ocean, wear a wetsuit and watch for rip currents.

What to pack for July

• Summer clothes for warm afternoons.
• A sweater or light jacket for cool mornings and evenings in the 50s.
• A warm jacket and long pants for San Francisco, Half Moon Bay or a foggy evening on the ridge.
• Sun protection. A brimmed hat and sunscreen for exposed trails.
• Water. Carry more than you think you need on foothill hikes.

What July weather is good for

Steady sun makes July easy to plan. Our July trip guide lists concerts, the Fourth and other dated events. Weather-driven ideas:

1. Redwood hikes. Shaded, foggy canyons stay cool on the hottest days. See our redwood hikes guide.
2. Early bike rides. Ride the Bay Trail before the afternoon wind builds.
3. Evening walks at the bay. The Baylands are breezy and cool at sunset.
4. Picnics and patios. Dry evenings are reliable, but bring a layer once the sun drops.

When a heat wave does arrive, follow the city's advice in our heat waves guide and keep strenuous plans to the early morning.

Frequently asked questions