Summer gets all the headlines around here. The bait balls, the manta rays, the water so warm you can dive it in a shorty. And it earns them — a good July day in the Sea of Cortez is hard to beat. But if you ask our guides when they’d personally take a week off to go diving, most of them don’t say July. They say September, or October, or the first half of November.
There’s a reason for that, and it isn’t a secret so much as a thing most people never get around to asking. So here’s the honest month-by-month on why autumn might be the best window to dive San Carlos, and what you’re actually trading off if you come then instead of in the height of summer.
What autumn does that summer doesn’t
Three things line up in the fall, and they don’t all line up at the same time in any other season.
The water stays warm. The Sea of Cortez holds its summer heat well into autumn — the surface doesn’t really start cooling in earnest until later in the year, so September and October give you bath-warm water without the full ferocity of the August sun beating down on the boat deck between dives.
The visibility comes back. Summer’s warmth comes with a cost: plankton blooms that feed the whole spectacle also cut down how far you can see. As those blooms settle through the autumn, the water clears up. You give up a little of the peak-summer marine-life chaos and you get back the ability to actually see it coming.
And the crowds thin out. Once school’s back in and the peak-season rush is over, the boats are quieter and the sites feel like they’re yours. For underwater photographers especially, fewer divers in the water means fewer stirred-up clouds of silt and more room to work a subject.
Month by month
September
The tail of summer, and arguably the sweet spot. Water is still warm, the pelagic action from the summer hasn’t fully wound down, and visibility is on the way back up. The one thing to keep in your peripheral vision is weather — September sits inside the Eastern Pacific hurricane season, and while the Sea of Cortez is sheltered compared to the open Pacific side of Baja, a passing system can shuffle the schedule. In practice that usually means we move a dive rather than lose a day, but it’s the reason we watch the forecast closely this month.
October
If we had to circle one month, this is often it. The water is warm, the visibility is usually excellent, the storm risk is dropping off, and the sea lions at Isla San Pedro Nolasco are as entertaining as ever. Comfortable diving, clear water, quiet boats. It’s the month that makes people book the same week again the following year.
November
Early November keeps most of October’s virtues. As the month goes on the water begins to cool and you’ll want to think more seriously about thermal protection, but the trade for that is some of the best visibility of the whole year. If clear water matters more to you than the very warmest water, late autumn is a genuinely strong call.
What you give up by not coming in summer
We’d rather tell you this than have you find out after booking. Peak summer — roughly July into August — is when the Sea of Cortez puts on its wildest show. The bait balls, the biggest concentrations of pelagics, the warmest water of all. If your whole reason for coming is to witness a bait ball boiling the surface with dolphins and sea lions tearing through it, summer gives you the best odds, and autumn’s calmer, clearer water is a different kind of trip.
So it’s not that autumn is better full stop. It’s that autumn is better for a lot of divers — the ones who value warm-but-not-brutal conditions, clear water, and having the site to themselves over raw summer spectacle. Be honest with yourself about which diver you are, and the season picks itself.
How to think about thermal protection across the season
A rough guide, and no more than that, because everyone runs warm or cold differently. Through September and into October most divers are comfortable in a lighter suit than they’d expect. As November progresses and the water starts to drop, people who felt fine in a 3mm in October often want more. If you’re doing multiple dives a day — and on a trip with us you will be — err toward slightly more warmth than a single dip would call for. Being cold on the third dive of the day ruins the third dive of the day.
Planning an autumn trip
Autumn trips book up on a different rhythm than summer ones. Because so many divers default to the summer season, the fall can be easier to get the dates you want — but October in particular has become popular enough that it pays to plan ahead rather than assume it’ll be wide open.
If you’re weighing it up, take a look at our trip options and the calendar to see what’s already on the books. Our multi-day packages — the 3-day, 4-day and 7-day trips — all run through the fall, and if the dates you want aren’t showing, reach out and we’ll talk about a custom charter.
Come in summer for the spectacle. Come in autumn for the diving. Both are the right answer — it just depends what you’re after.