The hottest month in Niteroi is February when the average maximum temperature is 31°, average temperature is 27° and average minimum temperature is 24°.
The coolest month in Niteroi is July when the average maximum temperature is 25°, average temperature is 22° and average minimum temperature is 19°.
The longest days in Niteroi are in December, with an average of 13.5 hours of daylight per day. June has the shortest days with an average of 10.7 hours of daylight per day.
The sunniest days in Niteroi are in August which has the most hours of sunshine per day with an average of 7.8 hours of sunshine per day, making it a quite sunny month with some cloud cover. December has the least sunshine with an average of 5.3 hours of sunshine per day, making it a sunny month that is overcast at times.
The ultraviolet index is the highest in January when it reaches 15.4 and lowest in June when it reaches 5.6.
An ultraviolet index reading above 11 indicates an extreme risk of harm from unprotected sun exposure. Unprotected skin risks burning in less than 10 minutes. Take all precautions because unprotected skin and eyes can burn in minutes. Tanning will be safest before 10am and after 4pm but only with a good application of sun screen. For those with sensitive skin stay in the shade and wear protective clothing, a wide-brimmed hat, and UV-blocking sunglasses. Generously apply broad spectrum SPF 30+ sunscreen every 2 hours, even on cloudy days. Watch out for relections from water that may increase ultraviolet exposure.
The warmest sea water temperatures in Niteroi are found in February when they peak at 27° and lowest in August when they dip to 21°.
The sea is best for swimming between December and May when the temperature is above 24° which is warm and pleasant for relaxing and swimming for long periods.
The wettest month in Niteroi is July with 2.3cm of rain and November has the most days of rain with 15.1 days with some rain, a wet time to visit the beach.
The driest month in Niteroi is January with 0cm of rain and August has the fewest days of rain with 5.8 days with some rain, a dry time to visit the beach.
The most humid month in Niteroi is January with a dew point (an indicator of humidity) of 24° which is very uncomfortable and fairly oppressive unless you are on a beach. At night you would most likely require airconditioning.
The least humid month in Niteroi is July with a dew point of 19° which is somewhat uncomfortable for most people in cities but fine on a beach.
The most windy month in Niteroi is October when the average maximum windspeed is 26kmh and the average wind speed is 11kmh.
The least windy month in Niteroi is May when the average maximum windspeed is 20kmh and the average wind speed is 9kmh.