Brunei has a mainly tropical rainforest type of climate (Köppen climate classification Af). The climate is hot and humid, with ample rainfall for much of the year. At high altitudes, the climate is humid subtropical, with heavy rainfall. Brunei occupies hardly 1% of the northern coast of Borneo, an island in Southeast Asia. The East Malaysian state of Sarawak surrounds and divides Brunei into two parts. Brunei has a coastline of 165 miles with the South China Sea on its northern coast. The location in the equatorial tropics and the Southeast Asian wind systems govern the climate. The equatorial location gives Brunei an equal duration of days and nights throughout the year.
Brunei is a small country with a total area of 2226 square miles, just 4°N of the equator. Much of the terrain near the coast is a flat plain. Mountains rise in the east, and low hills comprise a large section of the west. The Borneo rainforests cover much of the inland regions of Brunei. Belait is the longest river with a length of only 20 miles. Bukit Pagon is the highest point in Brunei at 1850 meters. Brunei lies in the Inter-Tropical Convergence Zone near the equator, where the air masses from the northern and southern hemispheres meet. The southwest monsoon arrives during the period from June to September. The northeast monsoon is active from December to March. The orographic effect is prominent and brings 3657.6mm (144") to 4064mm (160") of rainfall in the mountains. Heavy rainfall occurs in short periods. Thunderstorms peak from April to May and September to November.
Brunei has two main seasons separated by two transitional periods. The dry season from February to April is scorching and receives relatively low rainfall. The wet season from October to January is hot and humid and receives abundant rainfall. Summers are severely hot and register a moderate amount of rainfall. March to September is usually hot, with high solar heating and a decrease in cloudiness and rainfall. The average high temperatures reach a peak of 32.8°C (91°F) in May, with many days above 37.8°C (100°F). Temperatures are usually in the hot range of 24°C (75.2°F) to 36°C (96.8°F) in the dry season. Winters are warm and sunny but bring plenty of rain. The temperatures in the wet season usually range between 20°C (68°F) to 28°C (82.4°F). The average low temperatures drop to 22.8°C (73°F) in January, with few days below 21.1°C (70°F). The skies remain overcast for much of the year. Brunei lies in the doldrums, where the northeast and southeast trade winds meet to create calm weather amid low wind speeds.
Brunei receives abundant average annual rainfall between 2921mm (115") and 3048mm (120"). The wettest period from October to January brings more than 1270mm (50") of precipitation, with the maximum rainfall in December. A second maximum occurs from May to mid-June. The first minimum occurs during the driest period from February to April, which receives at least 508mm (20") of rain. Late June to August experiences the second minimum. Brunei sees 205 rainy days in the year. The annual sunshine is more than 2550 hours, and the average daily sunshine lasts between 6.3 hours and 8 hours. The sunshine is intense, with the ultraviolet index at the peak of 12 much throughout the year. The average relative humidity remains above 85% and creates an uncomfortably high heat index. The average seawater temperatures are in the warm range of 26.7°C (80.1°F) to 30°C (86°F), which are suitable for swimming throughout the year. The average daily wind speeds are in the mild range of 7.4km/h (4.6mph) to 11.7km/h (7.3mph). December to March is the windiest part of the year in Brunei.
The record for the highest temperature in Brunei is 39.4°C (102.9°F). The lowest temperature on record is 14.4°C (57.9°F).
The best time to visit Brunei
The best time to visit Brunei is from January to March when the rain is relatively low, and the temperatures are bearable. February and March are dry, sunny, and the least wet months of the year. Visitors are fewer during the early part of the year, and there is plenty of space on the beaches. The humidity is relatively less than the summer, and the conditions are favorable for outdoor activities. Cold air masses from Siberia occasionally penetrate Brunei's shores during the northeast monsoon to bring low minimum temperatures.
The worst time to visit Brunei
The worst time to visit Brunei is during the extremely hot period between June and August. The rainfall is relatively less, but the heat is oppressive, and the humidity increases the heat index to high levels. The extreme heat makes people flee to the mountains rather than the lowlands of Banda Seri Begawan. The rainforests see plenty of visitors but are very humid in the summer months. The sticky weather makes the conditions challenging for people from cold countries.
Brunei experiences weather hazards, such as floods, droughts, typhoons, and earthquakes. Tropical cyclones are frequent in the western Pacific during the southwest monsoon season. The storms originate in the equatorial and tropical waters and generally travel northwest to pass over the South China Sea to the north of Brunei. Squalls form over the Brunei waters as the strong southwesterly winds pass over them during tropical cyclones. The gusty winds significantly swell the waters and make the seas rough for navigation. Thunderstorms and heavy rainfall often accompany the squalls, but wind speeds rarely rise above 64.4km/h (40mph). Burning of slash and forest fires in the nearby islands of Indonesia are troublesome during the haze season from September to November. Brunei lies in the Pacific Ring of Fire, but mostly encounters earthquakes of mild intensity.
Weather in January
January is the coldest month of the year in Brunei, with average temperatures in the warm range of 22.8°C (73°F) to 30°C (86°F). Bandar Seri Begawan, the capital, registers average temperatures between 23.3°C (73.9°F) to 30°C (86°F), with overcast skies 83% of the time. Temperatures in Kuala Belait are usually in the zone of 23.3°C (73.9°F) to 30°C (86°F). January brings ample rainfall between 203.2mm (8") to 304.8mm (12") in Brunei, with a chance of precipitation for 60% of the time. The relative humidity ranges between 70% and 95%, but it is less muggy than the summer months. The average seawater temperatures at 27.5°C (81.5°F) are suitable for swimming and the beaches for sunbathing. Evenings receive a light breeze as the average hourly wind speed remains at 11.3km/h (7mph). Wear breathable and loose-fitting clothes during the day. A light jacket and scarf are useful in the evening in hilly areas. Expect intense sunshine that lasts up to 6.5 hours amid 12-hour days in Brunei in January.
Weather in February
February is dry and sunny in the winter of Brunei, with less than 7 hours of daily sunshine. The sunlight is intense even in the winter, with the sunrise approximately at 6.30 a.m. and sunset at 6.30 p.m. Temperatures in Seria are usually are in the comfortable zone of 22.8°C (73°F) to 31.7°C (89.1°F). Afternoons are hot and the time of peak temperatures. The average temperatures in the country are in the 23.9°C (75°F) to 30°C (86°F), with cloudy skies for 80% of the time. The precipitation decreases rapidly from 177.8mm (7") at the beginning to 101.6mm (4") by the end of the month. The average hourly wind speeds decrease from 11.3km/h (7mph) to 8.4km/h (5.2mph) over the month. The wind direction is predominantly from the north from the South China Sea. The average seawater temperatures at 26.9°C (80.4°F) are the coolest of the year and enjoyable for water activities. February ends the short winter and the period of relatively low temperatures in Brunei.
Weather in March
March is the driest month of the year in Brunei, moderate rainfall between 101.6mm (4") and 127mm (5"). The average temperatures are in the warm 24.4°C (75.9°F) to hot 31.7°C (89.1°F) range, with at least 7.3 hours of daily sunshine. Kula Belait registers temperatures between 22.8°C (73°F) and 32.2°C (90°F), with overcast skies for 78% of the time. The daylight lasts for 12 hours, and the intense sunshine is an obstacle for outdoor activities during the afternoons. Evenings receive a light breeze at the most. The average hourly wind speeds register between 6.4km/h (4mph) and 9.7km/h (6mph) as they blow in a predominantly northern direction. The average seawater temperatures at 27.2°C (81°F) are pleasurable for prolonged periods. The ocean waters are calm and suitable for excursions. However, beach lovers should wear sun protection and preferably visit the beaches in the mornings and evenings. Expect the heat to rise significantly by the last week of the month. March is the last month to visit Brunei in comfortable conditions.
Weather in April
April is hot and sunny in much of Brunei, with moderate precipitation in the range of 127mm (5") to 177.8mm (7"). The average temperatures are in the hot zone of 24.4°C (75.9°F) to 32.2°C (90°F), with clear skies for only 18% of the time. Temperatures in the hilly regions are few degrees colder than lower places, such as Bandar Seri Begawan, which scales 33.3°C (91.9°F) during the day. April usually registers between 139.7mm (5.5") and 190.5mm (7.5") of rain. The possibility of a wet day increases from 44% to 56% over the month. The bright and intense sunshine lasts for 8 hours during the 12 hours and 18 minutes of daylight. The humidity levels between 75% and 95% lead to miserable days, especially with wind speeds below 7.2km/h (4.5mph). Late afternoon and early morning thunderstorms are the flavors of April weather. The seawaters along the South China coast are at a comfortable 28.9°C (84°F) and enjoyable for swimming and water activities. Brunei becomes very hot by the end of April.
Weather in May
May is the hottest month of the year in Brunei, with 7.5 hours of blistering sunshine during the long days. The average temperatures rise swiftly in the hot zone of 24.4°C (75.9°F) to 32.2°C (90°F). The sweltering heat often registers temperatures above 37.8°C (100°F), especially in the low-lying interior areas. Bandar Seri Begawan is cloudy for 88% of the time. The conditions are oppressive, with average humidity above 85%. The frequency of afternoon thunderstorms reaches a peak during May and is a significant contributor to the 203.2mm (8") to 254mm (10") of rainfall. Afternoon outings are avoidable as the daily highest temperatures register between 12 p.m. and 4 p.m. Exposure to the heat for long durations can cause sunstroke. The average hourly wind speeds remain below 8km/h (5mph) and do little to relieve the heat. Light summer clothing made of cotton, sweatshirts, and wide-brimmed hats are suitable for the hot weather. The third week of May is typically the hottest period of the year and an avoidable time for a visit to Brunei.
Weather in June
June lies in the hot summer season of Brunei, with intense sunshine and moderate rainfall. The southwest monsoon arrives in the country with full strength. The cloud cover sees a slight decrease from 85% to 80% of the time over the month. Tutong registers average temperatures in the 23.9°C (75°F) to 31.7°C (89.1°F) range, with a 100% chance of muggy conditions. The predominantly westerly winds blow at average hourly speeds between 5.6km/h (3.5mph) and 8km/h (5mph). The land heats quickly, which means the best time to step out, is after sunrise at 6.10 a.m. The average seawater temperatures at 30°C (86°F) are the warmest of the year and offer the best chance to escape the blistering heat. The five degrees drop in temperatures in the hilly areas attracts crowds as the heat index reaches new highs. June brings 177.8mm (7") to 203.2mm (8") of rainfall in 16 wet days in the month. An umbrella or rain jacket is a necessity during outdoor trips. June begins the peak tourist season with muggy conditions in Brunei.
Weather in July
July is hot and humid in Brunei, with no sign of respite from the oppressive heat. The only places of relief are the hilly areas above 1000 meters and the mild seawaters at 30°C (86°F). July has the lowest average low temperature of the year at 22.8°C (73°F). However, the average high temperature reaches 32.2°C (90°F), and many days record 35°C (95°F). Kuala Belait is hot between 23.9°C (75°F) to 31.1°C (88°F), and unbearable due to the high heat index. The interior areas are hotter than the coast, and the rainfall of 177.8mm (7") to 203.2mm (8") does not provide relief from the heat for prolonged periods. The average hourly wind speeds drop below 8km/h (5mph) and provide nothing more than a light breeze. The daylight is slightly over 12 hours by the end of July, and the sunshine lasts for 7 hours every day. Sweatshirts and shorts are better in the sticky conditions that induce much sweat. People unaccustomed to tropical weather should avoid the heat of Brunei in July.
Weather in August
August is hot and relatively dry in Brunei, with plenty of sunshine. The scorching sun keeps the daily highs between 29.4°C (84.9°F) to 31.7°C (89.1°F). Nights register average temperatures in the warm range of 22.8°C (73°F) to 25.6°C (78.1°F). Temperatures in Tutong are in the hot zone of 23.9°C (75°F) to 31.7°C (89.1°F), with ample sunshine. The bright sunshine registers for at least 7 hours during 12 hours of daylight. The skies remain overcast for 85% of the time, and the high average humidity above 85% keeps the conditions muggy. August sees 19 wet days, but the rainfall registers an average of 190.5mm (7.5") in the country, a little less by Brunei's standards. The dominant westerly wind blows at average hourly speeds of 7.7km/h (4.8mph). The chance of precipitation increases rapidly from 46% at the beginning to 54% by the end of August. The average seawater temperatures at 29.4°C (84.9°F) are warm, while the seas remain calm. The conditions are generally harsh during August in Brunei.
Weather in September
September is a transitional period reminiscent of the summer season in Brunei. The average temperatures are in the range of 23.3°C (73.9°F) to 31.7°C (89.1°F), with 6.5 hours of daily sunshine. Temperatures and humidity are high but comfortably lower than the peak summer. Kuala Belait records average temperatures between 23.9°C (75°F) to 31.1°C (88°F), with relative humidity between 70% and 95%. The precipitation picks up in the second half of the month to register between 228.6mm (9") to 304.8mm (12"). Visitors need to carry rain protection most of the time with 19 rainy days in the month. Thunderstorms occur from late afternoons to midnight. September 1 is the clearest day of the month, with clear skies for only 16% of the time. The average hourly wind speeds clock between 6.8km/h (4.2mph) to 7.2km/h (4.5mph), with a predominantly western direction. The seawaters are warm and enjoyable for prolonged periods, with average temperatures at 29.4°C (84.9°F). September sees a significant rise in precipitation in Brunei.
Weather in October
October begins the wet season in Brunei, with ample rainfall and generally humid conditions. The precipitation is to the tune of 254mm (10") to 304.8mm (12"), with at least 21 wet days in the month. Tourists need to wear raincoats or carry umbrellas, with the possibility of a wet day at least 67% of the time. The average temperatures are in the 23.9°C (75°F) to 31.1°C (88°F) zone, and the nights are mild and humid in the wet season. The seawaters at 29.4°C (84.9°F) are suitable for swimming and other water activities during dry patches of weather. October days are sticky with humidity in the range of 75% to 95%. The average hourly wind speeds range between 6.4km/h (4mph) to 7.2km/h (4.5mph) and blow westwards. The daily sunshine lasts for 6.5 hours during the 12-hour days. The sun's ultraviolet is at the peak of 12, even after the end of the summer. Tourists who visit Brunei in October need to bring both rain and sun protection accessories.
Weather in November
November brings abundant rainfall in Brunei during the northeast monsoon. Heavy rains lash the coast of Brunei and register at least 355.6mm (14") in the month. Thunderstorms are frequent from afternoon to midnight, but most of the precipitation is in the form of rain showers. The average temperatures hover in the 23.9°C (75°F) to 31.1°C (88°F) zone, with overcast skies up to 91% of the time. November 12, the cloudiest day of the year, has clear conditions only 9% of the time. The third week of November is the rainiest, with the chance of a wet day for 72% of the time. The daylight is a little short of 12 hours, and the sunset occurs by 6:08 p.m. during much of the month. Humidity levels are in oppressive and miserable zones and often reach 95% during the day. Sweatshirts are useful in the evenings. Expect nights to be mostly mild but humid. November vacations need to count in precipitation every day in Brunei.
Weather in December
December is the wettest month of the year in Brunei with 355.6mm (14") to 406.4mm (16") of heavy rainfall. The arrival of the winter season does not bring a substantial drop in temperatures. Winter days are often warm and humid, with at least a 63% chance of rain. Bandar Seri Begawan registers average temperatures in the 23.9°C (75°F) to 30.6°C (87.1°F) range, with only 6.5 hours of daily sunshine. December 21 is the shortest day of the year, with 11 hours and 50 minutes of daylight. Nights typically remain above 22.8°C (73°F) and often see thunderstorms and rain. The average seawater temperatures are enjoyable for swimming and other water activities at 28.9°C (84°F). Wind speeds increase from 9.2km/h (5.7mph) to 10.8km/h (6.7mph) by the end of December, and the direction is predominantly from the north. Umbrellas and raincoats are necessary, but pack sweaters only for hilly regions. Expect rain almost every day in the month. The last week of December provides fair weather in Brunei.