September weather forecast
Bolama, Guinea-Bissau

September

Weather in September

September ushers in an easing of rain with a drop down to 132mm (5.2"). During this period, Bolama begins to transition from the wet period back to the dry season. With less cloud coverage than the previous months, daylight hours begin to increase again. Sunshine takes a front seat again, relieving the city from heavy clouds and constant downpours. The weather during this month allows visitors to begin exploring outdoor activities as the rains recede, marking the beginning of the drier months ahead.

Temperature

The commencement of September brings an average high-temperature of a hot 30.5°C (86.9°F), marking an inconsequential divergence from August. September nights experience a consistent temperature drop to a warm 25°C (77°F).

Heat index

The heat index value for September is evaluated at a blistering 40°C (104°F). Use additional protective measures, heat cramps and heat exhaustion are possible outcomes. Continuous activity might lead to heatstroke.
Heat index determinations are made taking into account the shade and light air movements. Under direct sunshine, the heat index values might be elevated by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'apparent temperature' or 'felt air temperature', provides an understanding of perceived warmth by combining temperature and relative humidity. Elements of metabolic variation, physical activity, and clothing contribute to the effect of temperature on an individual. Understand that direct sun rays can influence the weather's impact, leading to an increase in the heat index by 15 Fahrenheit (8 Celsius) degrees. Heat index values are extremely significant for babies and toddlers. Kids are usually more vulnerable than adults, given their lesser sweating ability. Along with their larger skin surface relative to their small stature and the excess heat due to their activity, their risk is amplified.
In high temperatures, perspiration kicks in, allowing the human body to cool down through the evaporation of sweat. Under conditions of high relative humidity, the rate of evaporation decreases. This results in the body retaining more heat than under conditions of dry air. The body is at risk of dehydration and related complications when it fails to shed excessive heat.

Humidity

The average relative humidity in September in Bolama is 81%.

Rainfall

In Bolama, Guinea-Bissau, in September, it is raining for 20.7 days, with typically 132mm (5.2") of accumulated precipitation. In Bolama, during the entire year, the rain falls for 107.5 days and collects up to 726mm (28.58") of precipitation.

Sea temperature

In Bolama, in September, the average water temperature is 27.8°C (82°F).
Note: Water temperatures in the range of 25°C (77°F) to 29°C (84.2°F) are warm and delightful, ensuring comfort during water activities over extended periods.

Daylight

In September, the average length of the day in Bolama is 12h and 11min.
On the first day of September in Bolama, Guinea-Bissau, sunrise is at 06:51 and sunset at 19:11. On the last day of the month, sunrise is at 06:50 and sunset at 18:52 GMT.

Sunshine

In September, the average sunshine is 7.5h.

UV index

January through December, with an average maximum UV index of 7, are months with the highest UV index. January through December, with an average maximum UV index of 7, are months with the lowest UV index. A UV Index value of 6 to 7 symbolizes a high health risk from unsafe exposure to UV radiation for ordinary individuals.
Note: In September, a daily UV index of 7 turns into the following recommendations:
Implement preventive steps and embrace sun safety standards. Protection from skin and eye distress is compulsory. Be aware that the sun's UV radiation is strongest between 10 a.m. and 4 p.m. and try to reduce direct sun exposure during this period as much as possible. Using UVA and UVB-protective sunglasses and sun-protective clothing is effective against UV radiation. Caution! Sand and water reflections can notably increase the UV radiation intensity.

Frequently asked questions

How hot does it get in September?
September temperatures vary between a high-temperature of 30.5°C (86.9°F) and a low-temperature of 25°C (77°F). The average heat index (a.k.a. 'feels like', 'felt air temperature'), which combines air temperature and relative humidity, in September is evaluated at 40°C (104°F).
What is the average humidity in September?
In Bolama, the average relative humidity in September is 81%.
How much does it rain in September?
In Bolama, in September, during 20.7 rainfall days, 132mm (5.2") of precipitation is typically accumulated.
What is the water temperature in September?
In September, the average sea temperature is 27.8°C (82°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 Bolama have in September?
In September, the average day length is 12h and 11min.
When is the sunrise / sunset in September?
In September, on the first day of the month, sunrise is at 06:51 and sunset at 19:11. On the last day of the month, sunrise is at 06:50 and sunset at 18:52 GMT.
How many hours of sunshine does Bolama have in September?
In Bolama, the average sunshine duration in September is 7.5h.
What is the month with the highest UV index?
January through December, with an average maximum UV index of 7, are months with the highest UV index.
When is the lowest UV index?
January through December, with an average maximum UV index of 7, are months with the lowest UV index.
How high is the UV index in September?
In September, the average daily maximum UV index is 7. A UV Index value of 6 to 7 symbolizes a high health vulnerability from exposure to the Sun's UV radiation.
Average high temperature
Average low temperature
Average wind speed
Average max. wind speed
Average wind speed gusts
Average humidity
Average rainfall
Average rainfall days
Average sea temperature
Average daylight
Average sunshine
Average sunshine days
Average UV index
Average cloud cover
Average visibility
Average temperature in September
Bolama, Guinea-Bissau
  • Average high temperature in September: 30.5°C

The warmest month (with the highest average high temperature) is March (35.5°C).
The month with the lowest average high temperature is August (29.6°C).

  • Average low temperature in September: 25°C

The month with the highest average low temperature is June (26°C).
The coldest month (with the lowest average low temperature) is January (21.8°C).

Average pressure in September
Bolama, Guinea-Bissau
  • Average pressure in September: 1012.2mbar

The month with the highest atmospheric pressure is July (1012.9mbar).
The months with the lowest atmospheric pressure are March and April (1010.1mbar).

Average wind speed in September
Bolama, Guinea-Bissau
  • Average wind speed in September: 9.7km/h

The windiest month (with the highest average wind speed) is June (13.2km/h).
The calmest months (with the lowest average wind speed) are October and November (9km/h).

Average humidity in September
Bolama, Guinea-Bissau
  • Average humidity in September: 81%

The month with the highest relative humidity is August (82%).
The month with the lowest relative humidity is January (32%).

Average rainfall in September
Bolama, Guinea-Bissau
  • Average rainfall in September: 132mm

The wettest month (with the highest rainfall) is August (270mm).
The driest months (with the least rainfall) are January and February (0mm).

Average rainfall days in September
Bolama, Guinea-Bissau
  • Average rainfall days in September: 20.7 days

The month with the highest number of rainy days is August (26.9 days).
The month with the least rainy days is January (0.3 days).

Average sea temperature in September
Bolama, Guinea-Bissau
  • Average sea temperature in September: 27.8°C

The best month for swimming (with the highest average sea temperature) is November (28.6°C).
The coldest month (with the lowest average sea temperature) is February (25.4°C).

Average daylight in September /
Average sunshine in September
Bolama, Guinea-Bissau
  • Average daylight in September: 12h and 1min

The month with the longest days is June (Average daylight: 12h and 48min).
The month with the shortest days is December (Average daylight: 11h and 30min).

  • Average sunshine in September: 7h and 3min

The months with the most sunshine are March, April and May (Average sunshine: 9h and 54min).
The month with the least sunshine is August (Average sunshine: 6h and 6min).

Average sunshine days in September
Bolama, Guinea-Bissau
  • Average sunshine days in September: 8 days

The month with the most sunshine days is January (30.7 days).
The month with the least sunshine days is August (2.9 days).

Average UV index in September
Bolama, Guinea-Bissau
  • Average UV index in September: 7

The months with the highest UV index are January, February, March, April, May, June, July, August, September, October, November and December (UV index 7).
The months with the lowest UV index are January, February, March, April, May, June, July, August, September, October, November and December (UV index 7).

Average cloud cover in September
Bolama, Guinea-Bissau
  • Average cloud cover in September: 46

The month with the most cloud cover is August (Cloud cover 57).
The months with the least cloud cover are March and April (Cloud cover 7).

Average visibility in September
Bolama, Guinea-Bissau
  • Average visibility in September: 10km

The months with the highest visibility are January, February, March, April, May, June, September, October, November and December (10km).
The months with the lowest visibility are July and August (9km).

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