In July, typical afternoon highs at Alcatraz Island run around 63°F (mild). Mid-afternoon sun stands about 62° high, and the sun is up from 5:59 AM to 8:31 PM. Historic districts usually offer building shade on one side of the street as the sun moves.
See live sun & real shadows here →| January | 59°F |
| February | 59°F |
| March | 60°F |
| April | 62°F |
| May | 67°F |
| June | 65°F |
| July | 63°F |
| August | 69°F |
| September | 71°F |
| October | 69°F |
| November | 62°F |
| December | 56°F |
Historic districts usually offer building shade on one side of the street as the sun moves. See real building shadows over satellite imagery for any time of day: https://isthereshade.com/?anywhere&at=37.82667,-122.42278
Around 8:31 PM local time in mid-July (it shifts through the year). Sunrise is about 5:59 AM.
Alcatraz Island · San Francisco, CA. Data: exact sun position; climate normals from historical weather; live forecast on the interactive view.
Most people worry about the wrong thing on Alcatraz. The island sits in San Francisco Bay, ringed by water and swept by wind, and its climate is famously cool, so the question is less "how do I survive the heat" and more "how do I stay comfortable in the sun and wind while I walk a lot of exposed ground." The cellhouse tour and the paths up to it are largely open, with long stretches of pavement, ramps, and switchbacks between you and any cover.
San Francisco's numbers tell the story. Even in the warmest months the afternoon highs barely move: about 63°F in July, 69°F in August, and 71°F in September, which is actually the island's warmest stretch. There is no heat wave to plan around here. The sun, the glare off the water, and the wind are what you feel.
In July the sun rises around 5:59 AM and sets near 8:31 PM, and tours run through much of that window. At 3 PM in high summer the sun stands about 62 degrees up, off to the west-southwest, so the exposed walkways and the parade ground get direct light through the afternoon. Morning tours often start under bay fog that burns off toward midday; afternoon tours are more likely to be clear and bright, with that hard reflected glare coming off the water on all sides.
Because the island faces open water in every direction, there is no reliable building line to walk in the shade of on the way up. The dock area and the sun-away sides of the cellhouse and ruins offer the only consistent cover, and where that falls shifts through the day as the sun swings toward the west.
Inside the cellhouse you are out of the sun entirely, that is the coolest, most sheltered part of any visit. Outdoors, expect exposure: the switchback road, the gardens, and the overlooks are open, and the wind can make a bright 60-degree afternoon feel brisk rather than warm. The certain shade is structural, on the lee and sun-away sides of the old prison buildings, and it moves with the sun.
To see how the island's buildings and terraces cast shadow at your tour time, the satellite shadow view maps the shade footprint for a given date and hour.
Skip the heat-and-hydration checklist you would use in the desert, Alcatraz never gets hot. Instead, layer up. The ferry crossing and the exposed climb are windy and often cooler than downtown San Francisco, so a jacket earns its place even on a July afternoon. Sunscreen still matters: the overhead sun and the glare off the bay will catch you out on a "cool" day.
For the calmest light and thinnest crowds, an early tour is hard to beat, fog and all. If you want reliable clear views over the bay, the later-morning and early-afternoon runs tend to be brighter, just brace for wind and bring that layer.