January weather forecast
Surabaya, Indonesia

The weather in Surabaya during the first onset of the year ushers in a warm milieu with adequate cloud cover that provides optimal conditions for outdoor activities. It is slightly warmer than December, which offers a hint of continuity in the holiday cheer. January experiences strong winds and high humidity levels, which is indicative of an active wet season with significant rainfall events. As the month with the highest recorded rainfall of 172mm (6.77"), it is prudent to keep an umbrella at hand. Intriguingly, despite the presumed gloomy skies, the month still experiences an above-average duration of sunlight.

Temperature

January, February and July are the coldest months, with an average high-temperature of 30.1°C (86.2°F).

Heat index

The average heat index in January is evaluated at a very hot 37°C (98.6°F). Greater preventive actions are needed, heat exhaustion and heat cramps are likely. Persistent activity could provoke heatstroke.
Consider that heat index readings are for situations in the shade and light wind. A direct sunlight exposure may boost the heat index by 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'real feel' or 'felt air temperature', ties air temperature with relative humidity to produce the perceived temperature sensation. One's perception of temperature can vary depending on physical activity and individual heat sensitivity, influenced by factors like wind, attire, and metabolic variations. When exposed to direct sunlight, it's possible for the heat index to increase by as much as 15 Fahrenheit (8 Celsius) degrees. Heat index values are quite important for children. Kids often lack the knowledge about the necessity to take breaks and consume liquids. Thirst, as a late symptom of dehydration, necessitates the maintenance of hydration, particularly during enduring physical activities.
Perspiration is the human body's physiological response to high temperatures and is an attempt to lower body temperature through evaporation of sweat. With an abundance of moisture present in the air, the process of evaporation becomes less effective, and the body fails to cool down as it should, leading to the sensation of overheating. As body temperatures escalate without effective heat release, one might face dehydration threats.

Humidity

In Surabaya, the average relative humidity in January is 78%.

Rainfall

In Surabaya, during January, the rain falls for 27 days and regularly aggregates up to 172mm (6.77") of precipitation. Throughout the year, in Surabaya, Indonesia, there are 187.8 rainfall days, and 839mm (33.03") of precipitation is accumulated.

Sea temperature

In Surabaya, Indonesia, the average seawater temperature in January is 29.3°C (84.7°F).
Note: For activities in the water such as swimming or diving, temperatures from 25°C (77°F) to 29°C (84.2°F) are considered optimal for prolonged enjoyment without discomfort.

Daylight

In Surabaya, the average length of the day in January is 12h and 29min.
On the first day of the month, sunrise is at 05:16 and sunset at 17:48. On the last day of January, in Surabaya, sunrise is at 05:29 and sunset at 17:55 WIB.

Sunshine

With an average of 8.1h of sunshine, January has the least sunshine of the year.

UV index

The months with the highest UV index in Surabaya are January through December, with an average maximum UV index of 7. January through December, with an average maximum UV index of 7, are months with the lowest UV index in Surabaya. A UV Index value of 6 to 7 symbolizes a high health hazard from unprotected exposure to Sun's UV rays for the average person.
Note: An average maximum UV index of 7 in January leads to these recommendations:
Stay clear of intense sun exposure. Solar protection is of utmost significance. Stay in the shade and limit direct sun exposure between 10 a.m. and 4 p.m., when UV radiation is at its strongest. Remember, however, that not all shade structures provide full sun protection. To best shield against UV radiation, choose sun-safe garments and dependable sunglasses. Notice! The reflection of water and sand increases the UV radiation significantly.