Month-specific sea-surface temperature · Mexico
Cozumel Sea Temperature in September
30.4°C
86.7°F
In September, sea-surface temperature near Cozumel has a historical monthly average of 30.4°C. This is not the reading for any particular holiday date.
Across 2022–2025, the lowest and highest yearly September monthly means were 30.1–30.5°C. These are not daily extremes.
Previous month
August · 30.1°C
Change into September: +0.3°C
Next month
October · 30.1°C
Change into next month: -0.3°C
Can you swim or snorkel in Cozumel in September?
At 30.4°C our temperature-only guide describes the water as very warm water. Comfort depends on your cold tolerance, immersion time and wind. A historical average cannot determine whether conditions are safe on any given day.
Do you need a wetsuit?
Swimwear is usually enough; a rash guard adds sun protection.
Which beach should you choose?
Look for a beach sheltered from the actual forecast waves and wind on your visit. Exposure, currents and entry conditions vary even where water temperatures are similar. Follow local warnings.
Cozumel sits on the Mesoamerican Reef. Water stays warm year-round, but winter months are a few degrees cooler than late spring. Use the month sections below for typical averages, then check today's forecast before a drift snorkel.
Check the current waves, wind and snorkeling forecast →
A live forecast does not predict a future September. Check again close to your trip.
Waves and wind: recorded-model conditions for September
These figures come from a separately modelled, date-specific wind/wave backfill, not the NOAA SST series. A single observed season is not a climatological likelihood or a guarantee of safe conditions.
Morning calm hours
90%
Afternoon calm hours
86%
Historical coverage
September 2026
30 valid days
A “calm hour” meets fixed modelled wave/wind thresholds; neither visibility nor local currents, entry conditions or actual beach safety is measured here. Periods may differ by coast.
Data source and limitations
Source: Open-Meteo Marine API, MeteoFrance sea-surface temperature; 2022–2025. Marine model grid near 20.42, -86.92. Based on 3 yearly monthly means and 2160 recorded samples. Source methodology.
Modelled sea-surface temperatures do not establish underwater visibility, wildlife, calm currents or safe entry.