(monthly mean)
The point at La Saladita breaks in warm water. The swell that reaches it comes mostly from the south-southwest at long periods, and the tide is small. This page collects the sea's numbers in one place: water temperature by month, marine heatwaves, the swell and its long-term record, the tide, and how El Niño shows up in each. Each section links to the full analysis it comes from.
Boardshorts in every month.
Mean daily sea-surface temperature by calendar month, with the range that holds on 80% of days (10th to 90th percentile). The coolest water is in March and April; the warmest is July to September.
| Month | Mean °C | Mean °F | 80% of days, °C |
|---|---|---|---|
| Jan | 28.1 | 82.6 | 27.1–29.0 |
| Feb | 27.4 | 81.4 | 26.4–28.4 |
| Mar | 26.9 | 80.4 | 25.4–28.2 |
| Apr | 26.9 | 80.4 | 25.1–28.5 |
| May | 27.9 | 82.2 | 25.9–29.7 |
| Jun | 29.3 | 84.7 | 27.9–30.4 |
| Jul | 30.1 | 86.1 | 29.1–31.0 |
| Aug | 30.3 | 86.5 | 29.3–31.1 |
| Sep | 29.8 | 85.6 | 28.8–30.7 |
| Oct | 29.6 | 85.3 | 28.7–30.4 |
| Nov | 29.3 | 84.7 | 28.4–30.0 |
| Dec | 28.7 | 83.6 | 27.7–29.6 |
No month needs a wetsuit. Boardshorts or a rash top all year.
Even in March and April, nine days in ten are above about 25 °C. A thin top is a matter of taste on a long session in the coolest weeks, and of sun protection the rest of the year.
The water has warmed by +0.13 °C per decade over 1982–2025 at this cell (95% interval 0.05 to 0.21). Two other sea-temperature products warm faster over the same years (ERSSTv5 +0.19, COBE-SST2 +0.21), so if anything this figure is low. The warmest year on record was 2023, 0.76 °C above the 1982–2025 mean; the coolest was 1988.
More heatwave days, and 2026 the most on record.
A marine heatwave here is at least five days in a row with the water above the 90th percentile for that time of year, measured against 1982–2011 (the Hobday et al. 2016 method, with the threshold pooled over an 11-day window either side of each date; gaps of up to two days are bridged). This is the method of the site's marine heatwave analysis, and the counts below are from it.
The busiest full years were 1990 (109 days), 2023 (106) and 2015 (103). In 2026 a short event ran 18–29 January and a long one ran from 13 May to 25 September: 136 days, more than twice the longest earlier event (57 days, December 2019 to February 2020). Every event in the record, including this one, is in the Moderate category. The 2026 count is recomputed on OISST through 25 October with the same threshold; the last two weeks of OISST are preliminary and can be revised.
A long-period south-southwest swell, with no trend.
Height, peak period and direction are 1994–2023 averages at the ERA5 ocean-wave node about 45 km offshore to the south-west; the height is for the whole sea, swell and wind waves together. Wave power is the 1979–2025 mean from the site's wave energy analysis: September is the strongest month (14.6 kW/m) and December the weakest (7.1). These are offshore values, not wave heights at the break.
No trend in wave energy or wave height.
Mean wave power is flat over 1979–2025 (−0.02 kW/m per decade, p=0.85). Over 1994–2023, which starts after ERA5 began assimilating satellite wave heights in 1991–93, power changes by +1% per decade (95% range −14% to +7%) and wave height by +0.5% (−5.5% to +2.9%). Neither is distinguishable from zero.
Long-period swell days
On a generic filter, a day when the offshore ERA5 wave height averages at least 1.0 m and the peak period at least 12 s, the node sees about 284 such days a year (1994–2023), with no trend (−1.1 days per decade, 95% range −27 to +18). The filter is a property of the offshore model, not a surf rating: it does not check direction, wind or tide, and the thresholds are on the ERA5 scale. For how swell size maps onto the ride at the point, see how the wave links up.
A small, mixed tide, mainly twice a day.
The tide is mixed, mainly semidiurnal (form factor 1.19): two highs and two lows on most days, unequal in height. The daily range, highest high to lowest low, averages 0.47 m on the model, and probably about 0.50 m in 2026–27 once the 18.6-year lunar cycle is allowed for. Spring tides reach about 0.64 m (the 90th percentile of days) and the largest day of the year is 0.75 m. Because the solar part of the tide is stronger than the lunar part at this gauge, the lows fall at about 1–4 am and 1–4 pm in every month, so dawn is usually a high or rising tide. Details are on the tide clock.
El Niño shows in the water, not clearly in the swell.
The two warmest years in the record, 2023 and 2015, were El Niño years, and they are two of the three years with the most heatwave days (1990 is the third). In the swell the link is weak: winter (December–February) wave power tends to run higher in El Niño winters, but the correlation is small and not distinguishable from zero (Spearman ρ = 0.25, 95% range −0.07 to 0.55, 43 winters, 1981–2023), and it is absent for the year as a whole (ρ = −0.01).
The sea-temperature cell (17.875°N, 101.875°W) is about 12 km west-south-west of the beach, because the cell at the coast is masked as land on the 1/4° grid. Water in the surf zone can run warmer or cooler than this offshore value by a few tenths of a degree, more during upwelling or strong onshore wind.
The wave values are from a reanalysis at a deep-water node 45 km offshore, not from a buoy or the break. The 2024–2025 peak periods are missing from the ERA5 record at this node, so period-based figures end in 2023.
The tide is a 33-constituent fit to 2011–2013 hourly gauge data at Zihuatanejo (fit error 6.4 cm), without nodal corrections. It describes the water level, not how the wave responds to it.
Sources and method
- Water temperature: NOAA OISST v2.1 daily, 1982–2025, cell 17.875°N, 101.875°W; monthly means and 10th–90th percentiles of daily values from the site's SST climatology. Warming trend and the two comparison products from the marine heatwave analysis.
- Marine heatwaves: Hobday et al. 2016 detection and Hobday et al. 2018 categories, 1982–2011 baseline, 90th-percentile threshold pooled over ±11 days, five-day minimum, two-day gap bridging. 1982–2025 figures are from the published analysis; the 2026 count was recomputed with the same code on OISST through 25 October 2026, after checking that the same code on the same series reproduces the published 129 events and 1,475 heatwave days for 1982–2025.
- Swell: ERA5 ocean waves from the Open-Meteo marine archive with the model pinned (
models=era5_ocean), hourly, at the node 17.5°N, 102.0°W. Height, peak period and power-weighted direction are 1994–2023 means; the 1994–2023 trends, including the long-period day count, are Theil-Sen slopes with a five-year moving-block bootstrap for the 95% range. Wave power, its monthly cycle and the 1979–2025 trend are from the wave energy analysis. The El Niño link uses the December–February Oceanic Niño Index. - Tide: the site's harmonic model of the UHSLC Zihuatanejo gauge (station 687), the same one the forecast uses; ranges from the tide clock for October 2026 – September 2027.
Analysis run: 27 October 2026.
Cite as: "The sea at La Saladita: water temperature, swell and tide", La Saladita Field Guide, lasaladita.com/findings/the-sea/, 2026-10-27.