April weather forecast
São Luís, Brazil

April carries on the pattern of high rainfall in São Luís, with the volume peaking at 476mm (18.74"). Despite significant levels of precipitation, temperatures slightly rise, leading the mercury from 23.1°C (73.6°F) to 29.6°C (85.3°F). The UV index remains unchanged from the previous months, persistently flagging a 12. As days slightly shorten to 12.1 hours of daylight, April stands as the wettest month of São Luís, compounding humidity with warm temperatures.

Temperature

April's commencement in São Luís is accompanied by an average high-temperature of a still warm 29.6°C (85.3°F), diverging marginally from March's 29.4°C (84.9°F). Throughout the April nights, São Luís encounters a low-temperature of 23.1°C (73.6°F).

Heat index

The average heat index in April is appraised at a very hot 39°C (102.2°F). Preventive measures are required to mitigate the risk of heat cramps and heat exhaustion. Continuous activity may precipitate heatstroke.
The standards for the heat index are set for locations in shade and under light breezes. Exposure to the sun directly might heighten the heat index by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'apparent temperature' or 'real feel', is a measure that combines air temperature and relative humidity into a single value that indicates how hot the weather feels. The individual's temperature perception can be influenced by numerous factors such as metabolic variations, physical activity, and clothing. Direct sun rays have a notable impact on perceived temperature, which can raise the heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are particularly relevant to children. Youngsters often neglect the necessity for rest and hydration. Thirst is a sign of advancing dehydration - thus the importance of maintaining hydration, specifically during long-lasting physical activities.
Perspiration, which is the evaporation of sweat, is a primary way the human body manages and dispels excessive warmth. Under high air temperature coupled with high humidity (high heat index), the body's perspiration is reduced, intensifying the sensation of heat. When heat uptake goes beyond the body's cooling mechanisms, there's a surge in body temperature, posing health risks.

Humidity

The most humid month is April, with an average relative humidity of 90%.

Rainfall

April is the month with the most rainfall in São Luís. Rain falls for 22 days and accumulates 476mm (18.74") of precipitation.

Sea temperature

In São Luís, the average seawater temperature in April is 28.6°C (83.5°F).
Note: With water temperature from 25°C (77°F) to 29°C (84.2°F), all water activities are comfortable and delightful, devoid of discomfort even for lengthened periods.

Daylight

In April, the average length of the day is 12h and 4min.
On the first day of the month, sunrise is at 05:58 and sunset at 18:03. On the last day of April, sunrise is at 05:53 and sunset at 17:55 -03.

Sunshine

In April, the average sunshine is 3.8h.

UV index

January through April, September through December, with an average maximum UV index of 12, are months with the highest UV index. A UV Index estimate of 11, and higher, represents an extreme health hazard from unprotected exposure to Sun's UV rays for the average person.
Note: In April, the maximum UV index of 12 suggests this advice:
Put into effect every precaution of importance, unprotected skin and eyes may get burns swiftly. Stay out of direct sunlight and seek shade between 10 a.m. and 4 p.m., when UV radiation is strongest, but remember that shade devices may not offer full sun protection. To cut down UV radiation exposure by about half, sport a wide-brim hat. Post an outdoor workout or swimming, a broad-spectrum SPF 30+ sunscreen should be applied generously and frequently. Caution! The mirror effect of sand and water ups the UV radiation strength.