September weather forecast
Cozumel, Mexico

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Palm trees and clear blue waters on Chen Rio white sandy beach in Cozumel, Mexico
Palm trees and clear blue waters on Chen Rio white sandy beach in Cozumel, Mexico

Weather in September

In September, the weather in Cozumel begins a gradual transition towards the cooler months. A slight dip in daylight hours is compensated by increased sunshine, providing abundant hours for outdoor pursuits. The UV index drops to 11, but sun protection remains a must. Torrential showers grace the city in September, where the monthly rainfall achieves a maximum of 240mm (9.45").

Temperature

Cozumel, Mexico, notes an average high-temperature of a still hot 31.9°C (89.4°F) in September, displaying minor variation from August. Throughout September, Cozumel's nights cool down to an average of 23.6°C (74.5°F).

Heat index

September's heat index is computed to be a life-threatening hot 47°C (116.6°F). Stay vigilant: Heat cramps along with heat exhaustion are expected. Heatstroke may follow prolonged exertion.
Records show heat index calculations are tailored for shaded regions and mild winds. The heat index has the possibility to be enhanced by 15 Fahrenheit (8 Celsius) degrees when there is direct sun exposure.
Note: The heat index, also known as 'felt air temperature' or 'apparent temperature', evaluates the perceived heat by adding the effect of moisture in the air. Factors such as metabolic variation, pregnancy, and physical activity play a role in one's impression of weather. You should know that direct sun exposure can heighten weather effects, potentially elevating the heat index by 15 Fahrenheit (8 Celsius) degrees. Heat index values are particularly relevant to children. Young individuals usually face greater risks than adults as their sweat production is less. Also, their larger skin surface relative to their small bodies and the high heat generation due to their activity contributes to their vulnerability.
Perspiration is the human body's physiological response to high temperatures and is an attempt to lower body temperature through evaporation of sweat. In the presence of high relative humidity, the evaporation rate diminishes, resulting in the body retaining more warmth compared to dry conditions. If heat absorption isn't effectively countered by the body's cooling methods, body temperature surges, hinting at potential problems.

Humidity

The most humid month in Cozumel is September, with an average relative humidity of 87%.

Rainfall

In Cozumel, in September, during 15.4 rainfall days, 240mm (9.45") of precipitation is typically accumulated. Throughout the year, there are 119.9 rainfall days, and 1490mm (58.66") of precipitation is accumulated.

Sea temperature

July through October, with an average sea temperature of 29°C (84.2°F), are months with the warmest seawater.
Note: Water activities in surface temperatures between 25°C (77°F) and 29°C (84.2°F) are seen as exceptional and extremely agreeable for lengthened time spans.

Daylight

In Cozumel, the average length of the day in September is 12h and 15min.
On the first day of September, sunrise is at 6:31 am and sunset at 7:02 pm. On the last day of the month, sunrise is at 6:38 am and sunset at 6:36 pm EST.

Sunshine

September and November, with an average of 6.1h of sunshine, are months with the least sunshine.

UV index

In September, the average daily maximum UV index is 11. A UV Index value of 11, and more, symbolizes an ultimate health vulnerability from exposure to the Sun's UV radiation for the ordinary person.
Note: The UV index of 11 in September translates into these instructions:
Adopt every vital precaution, unprotected skin and eyes may burn rapidly. During the period from 10 a.m. to 4 p.m., UV radiation is highest. Try to avoid direct sunlight during these hours. For optimum UV protection, wear sun-resistant attire complemented with a hat and quality shades. Even when the sky is cloudy, apply generously and frequently reapply a sunscreen with SPF 30 or more, especially post every swim or outdoor exercise. Attention! The reflection of both water and sand can increase the intensity of UV rays.

Frequently asked questions

How hot is it in Cozumel in September?

During September, Cozumel experiences an average high-temperature of 31.9°C (89.4°F) and a low-temperature of 23.6°C (74.5°F). The average heat index (a.k.a. 'felt air temperature', 'apparent temperature'), which calculates the temperature value influenced by the moisture in the air, in September is computed to be 47°C (116.6°F).

What is the most humid month?

September is the most humid month, with an average relative humidity of 87%.

What is the average humidity in September?

In September, the average relative humidity is 87%.

How much does it rain in September?

In Cozumel, during September, the rain falls for 15.4 days and regularly aggregates up to 240mm (9.45") of precipitation.

When is the sea warmest?

July through October, with an average sea temperature of 29°C (84.2°F), are months with the warmest seawater.

What is the sea water temperature in September?

In Cozumel, in September, the average water temperature is 29°C (84.2°F). Water temperature between 25°C (77°F) and 29°C (84.2°F) is regarded as very warm and enjoyable by all. With these temperatures, water activities are pleasurable, without feeling uncomfortable for prolonged periods.

How many hours of daylight does Cozumel have in September?

In Cozumel, the average day length in September is 12h and 15min.

When are sunrise and sunset in September?

On the first day of September, sunrise is at 6:31 am and sunset at 7:02 pm. On the last day of the month, sunrise is at 6:38 am and sunset at 6:36 pm EST.

What is the month with the least sunshine?

September and November, with an average of 6.1h of sunshine, are months with the least sunshine.

How many hours of sunshine does Cozumel have in September?

In Cozumel, the average sunshine duration in September is 6.1h.

What is the UV index reading in September?

The average daily maximum UV index in September is 11. A UV Index estimate of 11, and higher, represents an ultimate hazard to health from unprotected exposure to UV radiation.
Average humidity
Average rainfall days
Average daylight
Average sunshine
Average UV index

Average temperature in September
Cozumel, Mexico

Average temperature in September - Cozumel, Mexico
  • Average high temperature in September: 31.9°C

The warmest month (with the highest average high temperature) is August (33°C).
The months with the lowest average high temperature are January and December (28.6°C).

  • Average low temperature in September: 23.6°C

The month with the highest average low temperature is June (23.8°C).
The coldest months (with the lowest average low temperature) are January and February (19.4°C).

Average humidity in September
Cozumel, Mexico

Average humidity in September - Cozumel, Mexico
  • Average humidity in September: 87%

The month with the highest relative humidity is September (87%).
The months with the lowest relative humidity are March and April (79%).

Average rainfall in September
Cozumel, Mexico

Average rainfall in September - Cozumel, Mexico
  • Average rainfall in September: 240.2mm

The wettest month (with the highest rainfall) is October (242.5mm).
The driest month (with the least rainfall) is March (32.2mm).

Average rainfall days in September
Cozumel, Mexico

Average rainfall days in September - Cozumel, Mexico
  • Average rainfall days in September: 15.4 days

The month with the highest number of rainy days is October (15.7 days).
The month with the least rainy days is April (3.7 days).

Average sea temperature in September
Cozumel, Mexico

Average sea temperature in September - Cozumel, Mexico
  • Average sea temperature in September: 29°C

The best months for swimming (with the highest average sea temperature) are July, August, September and October (29°C).
The coldest months (with the lowest average sea temperature) are February and March (26°C).

Average daylight in September /
Average sunshine in September
Cozumel, Mexico

Average daylight in September / Average sunshine in September - Cozumel, Mexico
  • Average daylight in September: 12h and 2min

The month with the longest days is June (Average daylight: 13h and 24min).
The month with the shortest days is December (Average daylight: 10h and 54min).

  • Average sunshine in September: 6h and 1min

The month with the most sunshine is April (Average sunshine: 8h and 36min).
The months with the least sunshine are September and November (Average sunshine: 6h and 6min).

Average UV index in September
Cozumel, Mexico

Average UV index in September - Cozumel, Mexico
  • Average UV index in September: 11

The months with the highest UV index are April, May, June, July and August (UV index 12).
The months with the lowest UV index are January and December (UV index 7).

Cozumel, Mexico

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