It is Monday, June 1, at 7:45 AM. Somewhere on the Bay Bridge, a commuter in a fleece is squinting into a wall of gray. In the Mission, a barista is wearing a beanie. At Ocean Beach, the visibility is approximately one block. At the top of the Caldecott Tunnel, on the Oakland side, the marine layer is pressed up against the ridge like batting in a quilt — thick, gray, refusing to move.
Meanwhile, on the east side of the tunnel, in Lamorinda, the sun is already hitting the ridge above the Lafayette Reservoir. It is 64 degrees. There is no fog. There has not been fog. A person in a t-shirt is on the rim trail. They are smug. They are deeply smug. They have earned it by paying approximately $1.6 million for a three-bedroom on Glenside, and the marine layer staying west of the ridge is part of what they are paying for.
Welcome to June Gloom on the smug side of the tunnel.
The Fog Dam
Here is the actual meteorology, briefly: in May and June, the inland California valleys heat up faster than the cold Pacific does. The hot inland air rises, cool ocean air gets pulled inland to replace it, and as the marine air crosses the cool Pacific it condenses into a low cloud deck — the marine layer. In Southern California they call the worst stretches of it “May Gray” and “June Gloom.” In the Bay Area we mostly just call it “the fog,” and we have a strong opinion about which days have it and which don’t.
The Berkeley Hills run roughly north-south, capping out around 1,500 feet at Grizzly Peak. When the marine layer is shallow — typical for early June — it can’t get over the ridge. So the fog sits up against the western face of the hills, fills in Oakland, fills in Berkeley, fills in Emeryville, fills in everything west of the ridge, and stops. Right at the ridge. Like it’s been told.
The Caldecott Tunnel goes through the ridge. You drive into the west portal at 60 degrees and gray. You drive out the east portal at 68 degrees and sun. The temperature difference, on a June morning, is sometimes ten degrees in three quarters of a mile. There is no other commute in America where you can change climate zones inside a tunnel.
Lamorinda residents know this. Lamorinda residents exploit this. The June morning drive into the city is a kind of involuntary downgrade — you go from sun to fog, from 68 to 60, from “open the windows” to “where did I leave the jacket.” The reverse drive at 6 PM, when you come back through the tunnel and the east side is still in late-afternoon sun, is one of the small daily luxuries of living here. People talk about it. People mention it at parties. I tell people about it now, they will say, casually, as if they did not move here in 2019 specifically because their cousin told them about it.
The June Gloom Microhabits
By the second or third year in Lamorinda, you have unconsciously developed June-specific habits that you do not have in any other month:
- You check the fog cam at Grizzly Peak before any morning commitment in Oakland or San Francisco. You know which webcam. You don’t tell people.
- You leave a hoodie in the car — not in the closet, in the car — from June 1 through about August 10. The car hoodie is for crossing the tunnel. The house hoodie is for nothing because the house is 71 degrees and the windows are open.
- You make outdoor weekend plans for after 10 AM if they involve going west, and anytime at all if they involve staying east.
- You start saying “it’s beautiful here” with a specific intonation that means “I am aware Oakland is in a cloud right now.”
- You stop using the Weather app on your phone, because the Weather app — keyed to your home zip code — tells you it is 72 and sunny, which is true, but doesn’t help you know what your friend’s backyard birthday party in Rockridge is going to feel like at 1 PM. (Cloudy. It is going to feel cloudy.)
The Backyard Birthday Calibration Problem
This is the central practical hazard of June in Lamorinda: you get invited to things on the other side of the hill, and you forget the marine layer exists.
A Saturday afternoon birthday party in Berkeley. A graduation brunch in Piedmont. A “just come hang out in the backyard” thing in Oakland. You will dress for Lamorinda weather — shorts, a t-shirt, the espadrilles — and you will arrive shivering, on a lawn, in a 60-degree drizzle that the host is gamely pretending is fine. The host, who lives in Berkeley, is wearing pants and a long-sleeve henley because they live in Berkeley and they know. You will sit there in your shorts, smiling, internally calculating how soon you can leave without seeming rude. The answer is ninety minutes. You will leave in ninety minutes.
The reverse is also true and is harder to admit: when Bay Area friends come here for an event in June, they show up in fleeces, and by 1 PM they are visibly overheating in your backyard, and you have to find them a t-shirt from the drawer of t-shirts you keep for this exact reason. (The drawer exists. Every Lamorinda household with a pool club membership has the drawer.)
The Local Lie We All Tell
Lamorinda residents pretend not to enjoy this. We have a script. “Oh, we get the fog too sometimes,” we say, when somebody from the Bay Area brings it up. “It comes through the gap by the reservoir.” “Orinda gets the worst of it.” “Last week we had three days of marine layer.”
This is, technically, true. Orinda — closer to the tunnel, lower elevation — does sometimes catch a thin overflow of marine layer on the deepest mornings. The gap south of the Caldecott does let some fog through. Three or four mornings a June, the whole valley wakes up under a thin gray lid that burns off by 10. Sometimes.
But the script obscures the much larger truth, which is: most June mornings, we are sitting in the sun while the rest of the Bay Area is in a cloud, and we know it, and we like it. The hoodie stays in the car. The lawn dries before 9 AM. The reservoir loop is golden at 7:30. The marine layer is a problem that, for us, mostly happens to other people.
The Tunnel Always Wins
The June Gloom usually breaks for good around the first hot stretch of the month — typically the second week, when the inland heat finally pulls hard enough to bake the marine layer back. There’s a specific day, every year, when the fog stops trying. You feel it on the commute. You drive west into the tunnel, brace for the gray on the other side, and — nothing. Just sun, all the way to Treasure Island. The hoodie can go back to the closet. Summer has started.
Until then, the marine layer will keep showing up at the ridge, hitting the wall, and turning around. And every Lamorinda resident with a south-facing window will continue to do the small, slightly embarrassing morning ritual: stand in the kitchen, look west toward the hills, see the gray pressing up against Grizzly Peak, see the east side bright with sun, take a sip of coffee, and think — quietly, smugly, with full awareness — one more day on the right side of the tunnel.
The fog cam confirms it. The hoodie stays in the car.
Welcome to June.
See also: Tunnel Psychology on the Caldecott as a regional state of mind, the Caldecott Tunnel guide for the practical commuter version, and Sunday the Morning After for how we got here.
