Palo Alto weather in June

June is the start of real summer in Palo Alto. The days are the longest of the year, rain is essentially gone and most afternoons reach the upper 70s or low 80s. Mornings can begin under a gray lid of marine clouds that burns away by late morning. Every so often the fog retreats, high pressure builds and a short heat wave pushes the city into the 90s.

The climate numbers here are NOAA's 1991 to 2020 climate normals for the Palo Alto station (USC00046646) on the flats at about 25 feet. NOAA rates the station's figures "representative" because of gaps in its record, so treat tenths as rough. Sun times are calculated for central Palo Alto for June 2027 and checked against published tables. None of this is a forecast. Our weather guide compares the whole year.

June by the numbers

NOAA does not publish a Half Moon Bay sea temperature. The ocean figure is its long term average for the buoy about 18 nautical miles west of San Francisco.

Dry season, fully arrived

June averages 0.10 inches of rain. The median June gets just a hundredth of an inch. Fewer than one day in a typical June has measurable rain. When it does rain, it is usually a rare late system early in the month or a stray thunderstorm drifting in from the south.

Instead, June is about heat and fire. The Palo Alto station averages 10.8 days at 80°F or hotter and 2.8 days at 90°F or hotter, a little more than July on average. Early summer heat waves are common because the ocean is still cold and the marine layer can collapse quickly when high pressure moves overhead. A 100°F day is rare, averaging about 0.1 days in June, or roughly once a decade.

The longest days

June has the most daylight of the year. Day length runs from about 14 hours 35 minutes on June 1 to about 14 hours 45 minutes at the solstice on June 21, 2027. The earliest sunrise, about 5:47 a.m., comes in the second week of the month. The latest sunset, about 8:34 p.m., comes in the last week.

Long evenings make June ideal for after-dinner walks and late hikes. Stanford posts summer hours of 6 a.m. to 7:30 p.m. for the Dish, so the Dish closes well before sunset. Midpen preserves stay open until half an hour after sunset.

June gloom, heat and air quality

June gloom

The marine layer is a near daily feature along the coast in June. Cold ocean water chills the air above it, low clouds form and the sea breeze carries them inland overnight. San Francisco often sits under gray skies until afternoon or all day. In Palo Alto the Santa Cruz Mountains block much of that flow. The usual pattern is a gray or hazy start, then sun by 10 or 11 a.m. On some evenings you can watch fog pour over the ridge near Kings Mountain and Woodside like a slow waterfall.

Heat

When the marine layer is shallow or absent, the Peninsula heats up. The foothills and the Stanford campus feel it first. The flats near the bay stay a few degrees cooler thanks to the afternoon breeze. Many older Palo Alto homes have no air conditioning. During heat advisories the city names its five libraries as cooling centers. Our heat waves guide covers what to do.

Fire weather and smoke

By June the grass in the hills is dry. Red Flag Warnings, issued by the National Weather Service when wind and low humidity combine with dry fuel, are possible from June onward. Stanford can restrict access to the Dish during them. Wildfire smoke can arrive any time a large fire burns upwind, though the worst Bay Area smoke events of recent years came in late summer and fall. Hot afternoons can also bring summer Spare the Air alerts for ozone. Check AirNow before hard exercise.

Microclimates: fog line, flats and foothills

June shows the region's microclimates at their sharpest. Moffett Field, on the bay in Mountain View, averages a June high of 75.9°F, nearly three degrees cooler than the Palo Alto station's 78.5°F. It also has fewer hot days, with 1.6 days at 90°F against 2.8 in Palo Alto. The bay breeze is the difference.

Inside town, the Baylands and neighborhoods east of Highway 101 get the breeze first. Downtown and Midtown are warmer and calmer. The Stanford campus and the foothills are warmest on a still afternoon, then cool fastest after sunset. Pearson-Arastradero, from about 275 to 775 feet, can feel hot and exposed by noon.

The ridge is another story. Skyline Boulevard, above 2,000 feet, often sits at the top of the fog. Some mornings it is in bright sun above a sea of cloud. Other mornings it is socked in and dripping while Palo Alto is clear. The coast side of the ridge, in redwood canyons such as Purisima Creek, stays cool and damp all summer.

How June compares with San Francisco and San Jose

June opens a gap of about 12 degrees between Palo Alto and downtown San Francisco. The city averages a June high of 66.5°F and spends many mornings under fog. Palo Alto averages 78.5°F. San Jose, farther from the ocean, runs slightly warmer than Palo Alto at 79.1°F with warmer nights.

The nights are close everywhere, in the low to mid 50s. That means a day trip to San Francisco can start warm in Palo Alto and end in a cold wind at 60°F. Our San Francisco day trip guide has tips for dressing for it.

The coast in June

NOAA's buoy west of San Francisco averages 53.5°F in June, barely warmer than in May. The Monterey buoy averages 55.8°F. No long term figure is published for Half Moon Bay, but the coast there is usually cool, foggy and breezy in June, with air temperatures in the 60s. Inside the bay, the Redwood City reading averages 69.1°F, more than 15 degrees warmer than the open ocean.

Visit the coast for fog-softened walks, tide pools and seafood, not for sunbathing. Bring a warm layer. Our Half Moon Bay day trip guide covers the beaches and harbor.

What to pack for June

• Summer clothes for afternoons in the upper 70s and 80s.
• A sweater or light jacket for mornings and evenings in the 50s.
• A real jacket for San Francisco or the coast.
• Sun gear. A hat, sunglasses and high SPF sunscreen. The June sun is the strongest of the year.
• A big water bottle for exposed foothill trails.

What June weather is good for

June's long, dry days suit almost any outdoor plan, with a nod to heat on the hottest afternoons. Our June trip guide covers commencement and other dated events. Weather-driven ideas:

1. Cool trails on warm days. Head for the redwoods and shaded canyons. Our shaded hikes guide lists the best.
2. Early swims. Rinconada Pool is open year-round. See our swimming pools guide.
3. Late evening walks. With sunset after 8:30 p.m., a downtown dinner can end with a stroll in daylight.
4. Book early. June is busy on campus. Rooms fill around graduation. If your dates are firm, you can compare Palo Alto hotels now.

On heat wave days, plan outdoor activity before 10 a.m. or after 6 p.m. and spend the middle of the day somewhere cool.

Frequently asked questions