California Dive Visibility Recap: May 2026 in Review

May 2026 was a month of swings for California divers. The month started with a state-wide algal bloom that was finally breaking after dominating late April. It ended with two significant NW swell events that hammered the Central Coast and Monterey, plus a warm-water signal that pushed San Diego surface temperatures to 67°F by the last week. The SpearFactor dive conditions tool produced its monthly intel through all of it, and the network of diver reports that feed back into the tool kept the model honest about what was actually happening below the surface.

This recap covers what the tool predicted, what the dive network reported, where the predictions hit, where they missed, and the lessons May produced going into June.

The Month at a Glance

• Early May: lingering red tide / algal bloom clearing across the state

• Week 1-2: rapid clearing trend, Orange County and Central Coast leading the recovery

• May 16: new moon - peak WSB spawn window, came in murkier than April due to surface turbidity

• May 16-17: NW swell event hit the weekend, wiped out the clearing gains in many regions

• Mid-week: partial recovery as the swell pattern eased

• May 22-24: second NW swell pulse - this one hit Central Coast and Monterey harder than expected

• Late month: warming signal continues, San Diego surface temperatures reaching 67°F

• Month closed with Memorial Day weekend conditions mixed - calm in Southern California, blown elsewhere

What the Tool Got Right

The SpearFactor conditions tool performed strongest at the broad calls - distinguishing diveable from blown-out conditions, identifying the calm windows between storm events, and tracking the post-bloom clearing trend through the first two weeks. The 5/5 baseline audit had the tool at roughly 72% range overlap and 58% midpoint accuracy within ±3 feet, and May appears to have held that baseline reasonably well.

• Bloom clearing trajectory in early May was tracked correctly across multiple regions

• Orange County recovery week (Crescent Bay 15-25 ft, Deadman's ~15 ft) matched predictions

• Central Coast strength through early-to-mid May matched the model output, with Monastery and adjacent zones producing the strongest visibility windows in the state

• San Diego's slower bloom clearing was correctly identified as the trailing region

• Diveable-vs-blown calls were essentially never wrong through the calm weeks

• Water temperature predictions tracked actual readings closely, including the 67°F warming signal

What the Tool Missed

The honest accounting: May produced several conditions the tool either under-predicted or struggled to capture in real time. The pattern matches the documented weaknesses from earlier calibration cycles, and gives us material to work with going forward.

• The May 16-17 NW swell magnitude was under-predicted in the day-ahead forecast - the actual surface impact was larger than the model expected

• Central Coast and Monterey vulnerability to the late-May swell was under-weighted - the model treated those regions as more protected than they actually were

• Lover's Point pea-soup conditions (6 ft surface to 6 ft at 35 feet depth - uniform soup top-to-bottom) following the swell were not flagged as severely as actual conditions warranted

• Spatially heterogeneous spots remained the consistent weakness - LJ Cove between reef pockets versus north side, Pt Lobos cove versus outer reefs - single numbers cannot capture a 5-25 ft spread across one named location

• Surface viz versus depth viz gap during the post-bloom period - the tool's surface-weighted prediction sometimes under-stated what was available below 25 feet, but also sometimes over-stated surface clarity

Region by Region

San Diego

San Diego was the slowest to clear from the early-May bloom. Marine Room ran 5 ft at the start of the month and Mission Pacific Point (MPP) was 10 ft in patches. By mid-month the clearing trend was visible, but late-May NW swell pulses pushed visibility back down. La Jolla Shores closing the month at <5 ft in the shallows and 8-12 ft at the surface captured the pattern: warming water, calmer entry, but persistent column turbidity. The 67°F surface temperature reading at month's end was the strongest warm-water signal of the spring.

Orange County

Orange County was the fastest to clear from the bloom. Crescent Bay reached 15-25 ft visibility in the first week and Deadman's held around 15 ft, with the recovery being noted as a 'big jump from last week.' Late-May NW swell brought conditions back down - Laguna sites running 8-13 ft with 1-3+ ft surf by week three. Point Conception's deflection of the NW pulses helped OC retain more usable diving than Monterey or Central Coast during the same windows.

LA and South Bay

LA and South Bay produced the most consistent mid-tier visibility through the month. Mid-week 12-20 ft at Palos Verdes was the baseline with some cloudier surface layers. Catalina front side was less impacted than Central Coast through the late-month swell events. Small Craft Advisories drove some of the late-month degradation but the region overall held up better than the northern zones.

Central Coast

Central Coast was the star of the state through early and mid-May, with North Monastery routinely producing 15-30 ft and Point Lobos outer reefs delivering consistently. The late-May swell events flipped that script - by the weekend of May 22-24 the region was running 10 ft visibility with kelp/algae stirred up and significant surge. Mill Creek on the Big Sur coast was hit particularly hard, dropping to 4 ft from stirred-up kelp fragments and sand despite flat calm surface conditions. The Central Coast collapse mid-week was the surprise of the month.

Monterey Bay

Monterey was inconsistent through the month and got the hardest hit at the end. Breakwater 15-20 ft shallow with 10 ft deep on calm days was the baseline. Late-May the bay collapsed: Breakwater dropped to 4 ft, Lover's Point ran pea soup top to bottom (6 ft at the surface and 6 ft at 35 feet - uniform soup). The bay's vulnerability to NW swell was sharper than the broader Central Coast model anticipated.

Tool Performance Lessons

Three calibration takeaways stand out from May 2026:

• Swell impact on Central Coast and Monterey is being under-weighted - the model treated these zones as more buffered from NW pulses than they actually are. Adjustment is needed for the wave-energy fallback in the no-SASS path

• Surface turbidity during active blooms is a compound condition the model still over-counts (the chl-vs-NTU double-counting issue) - work on a dampener is queued but not yet shipped

• Spatial heterogeneity at single named spots remains the consistent gap - site-tip text mitigates by directing divers to cleaner zones, but the headline number cannot capture a 20-foot spread within one location

What the Network Produced

The diver reports that fed back into the tool through May were the highest-quality input the system has had. Reports from members on the water - Laguna, La Jolla, Monastery, Mill Creek, Lover's Point - drove real-time calibration that algorithmic predictions alone cannot match. The pattern that emerged: the tool plus the network produces something neither produces alone. Members who submitted reports got the highest-confidence intel for their next trip; members who only consumed the predictions got useful but less calibrated information.

The Water Temperature Story

May 2026 surface temperatures progressed from the low-60s at the start of the month to 67°F at the south end by the close. That is 3-5 degrees above the 30-year May average and is consistent with the marine heatwave plus weakening El Niño pattern that has defined California's 2026 season. The warming signal was visible across all regions, though more pronounced in Southern California than the Central Coast or Monterey.

Below the surface, the thermocline was developing through the month but remained less defined than typical late-spring conditions. As June progresses the thermocline should sharpen, producing the 8-12 foot temperature drop between surface and 40 feet that defines summer California diving.

Carrying Forward Into June

• Tool calibration work continues on the swell-impact under-weighting at Central Coast and Monterey

• The chl-vs-NTU dampener is queued for development when local browser testing infrastructure is available

• Spatial heterogeneity at named spots will continue to be mitigated by site-tip text directing divers to cleaner zones within each location

• The diver report network is the strongest part of the system - more reports produce better predictions, and members are encouraged to keep submitting

• Water temperatures should continue climbing through June - expect 64-70°F surface ranges across Southern California by mid-month

Where That Leaves the Season

May 2026 produced a month of variable conditions that tested the dive conditions tool and the diver report network. The tool held its 72% baseline accuracy across most predictions, missed on a handful of swell-driven Central Coast and Monterey calls, and continues to need refinement on bloom-plus-NTU compound conditions. The network of reports kept it honest and provided the real-time calibration that made it useful in spite of the algorithmic gaps. Going into June, the data flow that drove May's accuracy is the same data flow that will drive June's. Members who report from the water make the system better for the next diver.

Check real-time California dive conditions at the SpearFactor dive conditions tool. Submit dive reports to keep the system calibrated. The next major calibration cycle will incorporate the May lessons into the model.