Laos has a mainly tropical climate, with landlocked geography in Southeast Asia. Significant portions of the western and southern regions experience a tropical savannah climate (Köppen climate classification Aw). A large strip from the west-central to the southeast region falls under the influence of the tropical monsoon (Köppen Am). The remaining one-third of the land in the north and east has a subtropical climate (Köppen Cwa, Cwb). Laos lies at the center of the Indochinese Peninsula. Vietnam lies in the east, Cambodia in the southeast, Thailand in the southwest and west, and Myanmar and China in the northwest. The latitudes, high mountains, and monsoonal rains influence the climate.
Laos is a tropical country between latitudes 14°N and 23°N, with a northwest-southeast orientation. The topography is mainly mountainous, with steep terrain. The Annamite Range stretches from northeast to east, while the Luang Prabang Range lies in the northwest. The northern region is mountainous, with elevations mostly above 500 meters, and narrow river valleys. The Xiangkhoang Plateau in the north consists of green mountains and fertile valleys with numerous rivers. The Bolaven Plateau in the south has an average elevation of 1000 to 1350 meters. The panhandle region in the south consists of large level areas. However, only 4% of the land area is arable. The Mekong River is the largest and marks much of the western border with Thailand. The Annamite Chain forms the eastern boundary with Vietnam. Phou Bia is the tallest peak in Laos with a height of 2818 meters above sea level.
Summers are hot, and winters are chilly in Laos. March to mid-May is the hottest period of the year. The average high temperatures reach a peak of 35°C (95°F) in April. Temperatures reach up to 42.2°C (108°F) in the center-south and 45°C (113°F) in the north. The days have high temperatures, but even the nights can be warm and oppressive. The Luang Prabang region in the north has a relatively mild climate, with warm to hot summers and cold winters. Frost is common in the highlands and mountains. The southern region has harsh summers and mild winters. The mountainous regions are wetter than the plains, particularly at an altitude above 1000 meters. The rainy season begins by mid-May and stretches up to October. November to February is cold and dry in the winter. The average low temperatures are in the 10°C (50°F) to 15.6°C (60.1°F) range at the peak of the cold season. Temperatures vary by altitude and are significantly lower in the mountains and uplands than the plains.
The annual rainfall in Laos ranges from 1270mm (50") to 1778mm (70") in the plains and exceeds 3048mm (120") on the high mountain slopes. The Bolaven Plateau receives the highest rainfall of 3810mm (150") annually. The Luang Prabang region sees an average of 159 wet days in the year. Vientiane, the capital in the center-south, registers 118 rainy days annually. August and September are the wettest months due to the additional effect of typhoons. December is the driest month. The annual sunshine is ample and registers between 2100 hours in the north to 2600 hours in the south. The daily sunshine lasts for 8 hours in the center-south and 9 hours in the far south in the winter. The monthly average relative humidity ranges from low 66% in March to a high of 84% in August. The sun's ultraviolet index remains in the dangerous zone of 11 to 12 throughout the year except for the moderate winter months.
The highest temperature on record for Vientiane is 41.1°C (106°F), while the record for the lowest temperature is 0°C (32°F).
The best time to visit Laos
The best time to visit Laos is from November to February in the mild winter season. December and January are particularly pleasant, with comfortable temperatures in the average range of 10°C (50°F) to 29.4°C (84.9°F). The usually intense sunshine is moderately strong in the winter months. Tropical storms may linger until November, while temperatures exceed 35°C (95°F) in February in many regions. The northeast monsoon is active during the winter months. However, the rainfall is modest, and the sunshine is adequate between 6 hours and 9 hours. Nights are cozy on the plains, but cold in the mountains and highlands.
The worst time to visit Laos
The worst time to visit Laos is from June to August in the wet season. The southwest monsoon contributes much of the annual rainfall, and the atmosphere is humid and hot. Cloudy skies rule the roost. The heat index is high, and the rainfall is heavy. Rainstorms frequently occur in the wet months. Each month of the rainy season has at least 18 wet days and receives more than 254mm (10") of rain. Road travel becomes difficult, especially in the highlands where cloudbursts can occur. Typhoons frequently occur between August and October and bring heavy precipitation.
Laos faces weather hazards like thunderstorms, floods, droughts, tropical storms, typhoons, and earthquakes. Thunderstorms and rainstorms frequently occur in the rainy season. Heavy rainfall significantly increases the risk of floods and mudslides. Droughts are frequent in the interior in the summer. Tropical cyclones of Southeast Asia often affect Laos between May and December. Typhoons from the South China Sea hit the northern parts of Laos more than the southern regions. Tropical storms from the Bay of Bengal reach as far as Laos, with sustained high wind speeds. The mountainous region is prone to seismic disturbances, although earthquakes of large magnitudes are rare.
Weather in January
January is mild to cold in the winter in Laos, with plenty of sunshine. Luang Prabang has cool average temperatures in the 13.9°C (57°F) to 27.8°C (82°F) range, with cloudy skies and dull weather. Days can be hot, even in the mountains. Nights on the mountain peaks remain above freezing in the winter. In the center-south, Vientiane has mild temperatures in the range of 16.1°C (61°F) to 27.8°C (82°F). Cold air outbreaks are fewer on the plains compared to the mountains. In the far south, Pakxe is warm to hot between 17.8°C (64°F) and 31.1°C (88°F). The daily sunshine lasts between 8 hours to 9 hours in the plains and 6 hours in the mountains. The skies remain clear up to 70% of the time, and the daylight lasts above 11 hours. The relative humidity is in the comfortable zone of 60% to 75%. Warm winter clothes are suitable for the mountains. A sweater or rain jacket is usually enough in the plains. January is pleasant in much of Laos.
Weather in February
February is a mild winter month in Laos, with 7 hours to 9 hours of daily sunshine. Luang Prabang is between 15°C (59°F) and 31.1°C (88°F), with warm days and cozy nights. Vientiane and Savannakhet register warm temperatures between 17.8°C (64°F) and 31.1°C (88°F). The average temperatures in the mountains of Boun Neua, at an altitude of 900 meters, are in the 10°C (50°F) to 25°C (77°F) range. The daylight is slightly short of 12 hours in Laos in February. The daily average wind speeds are in the modest range of 4km/h (2.5mph) to 5.6km/h (3.5mph), with a predominantly easterly direction. The skies remain clear up to 70% of the time. The conditions are comfortable, but the chance of a muggy day increases gradually to 25% by the month-end. The northeast monsoon brings little rain, and most regions register between 0.5 to 25.4mm (1") of precipitation. Expect bright sunshine and hot afternoons on the plains. A light sweater or jacket is enough in most places except the high mountains. February is a generally pleasant month to visit Laos.
Weather in March
March is hot and dry in Laos at the end of the mild winter season. In Vientiane and Savannakhet, on the western boundary along the Mekong River, the average temperatures are in the hot range between 22.2°C (72°F) and 33.9°C (93°F). Phongsali in the north is warm in 13.3°C (55.9°F) to 27.2°C (81°F) zone and registers up to 25.4mm (1") of rainfall. Luang Prabang sees hot days and mild nights, with average temperatures between 17.8°C (64°F) and 33.9°C (93°F). The daily sunshine ranges between 6 hours to 7 hours in the extreme north but lasts for 9 hours in the center-south. The skies remain clear up to 66% of the time. March has the lowest monthly average humidity of the year at 66%. The daily average wind speeds are at the highest of the year between 4km/h (2.5mph) and 5.8km/h (3.6mph) in the northern mountains. A light jacket is useful in the evenings, but sweatshirts are better in the day. March generally has fair weather, but the days can be hot in Laos.
Weather in April
April is usually the hottest month in the summer of Laos, with average high temperatures between 29.4°C (84.9°F) and 35°C (95°F). Luang Prabang registers average temperatures in the 21.1°C (70°F) to 35°C (95°F) range, while Attapu in the southeast is in the hot 25°C (77°F) to 35.6°C (96.1°F) range. Xam Nua in the northeast is relatively cool in the 16.7°C (62.1°F) to 30°C (86°F) zone. The sunlight lasts for 8 hours during the 13-hour days. The skies remain overcast for 50% to 70% of the time. The relative humidity remains in the moderate range of 60% to 72%. April sees 76.2mm (3") to 101.6mm (4") of precipitation amid at least 8 wet days in the month. Isolated thunderstorms occur in the mountains. The daily average wind speeds remain in the moderate range of 4km/h (2.5mph) to 6.4km/h (4mph). Light summer clothing offers comfort, but a rain jacket is useful in the mountains. The northern and eastern mountains offer fair weather in the hot summer in April in Laos.
Weather in May
May is hot, humid, and cloudy in Laos. The skies are overcast for 70% to 85% of the time. The heat index increases significantly with the relative humidity between 75% and 80%. The daily sunshine reduces to less than 6 hours, and the daylight lasts for 13 hours. Luang Prabang is considerably hot, with average temperatures in the 22.8°C (73°F) to 33.9°C (93°F) zone. Vientiane is hot and humid, with average temperatures in the 25°C (77°F) to 32.8°C (91°F) range. Attapu is hot and muggy between 25°C (77°F) and 33.9°C (93°F), with daily average wind speeds below 3.2km/h (2mph). The southwest monsoon reaches southern Laos by mid-May. Precipitation registers between 127mm (5") in the north and 254mm (10") in the south, with an average of 15 wet days in the month. Sweatshirts, light summer clothing, and a rain jacket are suitable for muggy and wet weather. Scattered thunderstorms occur in many places, especially in the second half of the month. May brings uncomfortably sticky weather in Laos.
Weather in June
June is humid, cloudy, and wet in Laos with the arrival of the southwest monsoon. The skies remain overcast for 90% of the time. The daily sunshine lasts hardly for 5 hours in much of Laos. June 20 is the longest day of the year in Vientiane, with 13 hours and 12 minutes of daylight. The relative humidity is between 70% and 85%, and the chance of a wet day is up to 60% in June. The rainy month brings up to 177.8mm (7") of precipitation in the north and 279.4mm (11") in the south. The average temperatures in Luang Prabang are between 23.9°C (75°F) and 32.8°C (91°F), while Phongsali does relatively better in the 20°C (68°F) to 27.8°C (82°F) range. Savannakhet registers average temperatures in the 25.6°C (78.1°F) to 32.2°C (90°F) zone but sees at least 18 wet days in June. Expect bright sunshine between wet periods. Avoid a June visit to Laos, especially the mountains where mudslides are common.
Weather in July
July is humid and wet in Laos, as the wet season brings abundant rainfall everywhere. Thunderstorms frequently occur, and heavy spells of rain often make roads impassable. The northern mountainous regions receive up to 228.6mm (9") of rainfall. Luang Prabang is hot and muggy between 23.9°C (75°F) and 32.2°C (90°F), with 4 hours of daily sunshine. The northeast and northwest hilly regions are warm and humid in the 20°C (68°F) to 27.2°C (81°F) zone. The center-south regions, including Vientiane and Pakxe, register average temperatures in the 24.4°C (75.9°F) to 31.1°C (88°F) range. The skies remain overcast up to 95% of the time and allow hardly 4 hours of daylight. Winds blow predominantly from west and south. The daily average wind speeds are less than 4km/h (2.5mph) in the north and 6.4km/h (4mph) to 9.7km/h (6mph) in the south. July is the muggiest month of the year in Attapu in the southeast. The stifling heat and abundant rainfall make the conditions unfavorable to visit Laos in July.
Weather in August
August is the wettest month of the year in Laos, with mostly cloudy skies and high humidity. In the north, Luang Prabang receives 226.1mm (8.9") of heavy rainfall, while Vientiane records a massive 335.3mm (13.2") in the south. August sees at least 20 wet days, partially due to the effect of typhoons. The typhoon season is at its peak, and tropical storms hit northern Laos particularly hard. The daily sunshine limits to 4 hours as the skies remain overcast up to 90% of the time. The daylight reduces from 13 hours in the beginning to 12.5 hours towards the end of the month. The average temperatures in Vientiane and Savannakhet are in the hot zone of 25°C (77°F) to 31.1°C (88°F). Wind speeds remain below 3.2km/h (2mph) in the northern mountains, the lowest of the year. The atmosphere is muggy, with the monthly average humidity at 84%, the highest of the year. The storm season and heavy precipitation keep tourists away from Laos in August.
Weather in September
September is hot, humid, and rainy in Laos, with mostly cloudy skies. However, the sun's ultraviolet index is at a peak of 12, even in the wet month. The daily sunshine lasts for 5 hours in the south and 6 hours in the north. The rainfall decreases from its peak to register an average of 165.1mm (6.5") in the north and 294.6mm (11.6") in the center-south. Xam Nua registers average temperatures in the comfortable range of 18.3°C (64.9°F) to 26.7°C (80.1°F). Luang Prabang is hot at 32.2°C (90°F) during the day and warm at 22.8°C (73°F) during the night. Pakxe in the south is hot and humid, with average temperatures in the 23.9°C (75°F) to 30°C (86°F) zone. The first week of September is the calmest period of the year in Vientiane, with daily average wind speeds at 6.9km/h (4.3mph). The autumn equinox brings 12 hours of daylight in Laos, but the daily sunshine remains below 6 hours. Expect a decrease in rainfall by the end of September in Laos.
Weather in October
October sees reduced heat and humidity at the end of the rainy season in Laos. The precipitation reduces significantly to register 76.2mm (3") in the south and 101.6mm (4") in the north. October sees up to 8 wet days, with the relative humidity in the 60% to 75% range. The northern mountain region registers average temperatures in the comfortable 15.6°C (60.1°F) and 23.9°C (75°F). Luang Prabang is relatively hot, with average temperatures in the 21.1°C (70°F) to 31.1°C (88°F) zone. In the far south, temperatures are usually between 22.8°C (73°F) to 31.1°C (88°F), but the skies remain clear up to 45% of the time. October sees an increase in daily sunshine that registers up to 6 hours in the north and 8 hours in the south. The daily average wind speeds register between 7.2km/h (4.5mph) to 7.9km/h (4.9mph) in Vientiane, and the wind direction is predominantly from the east. The frequency of typhoons reduces significantly by the second half of October in Laos.
Weather in November
November is warm and relatively dry in Laos after the return of the southwest monsoon. The skies remain clear up to 60% of the time, and the daily sunshine lasts for 6 hours to 8 hours. The daylight decreases from 11.5 hours to register slightly more than 11 hours by the end of the month. The northern mountain regions of Phongsali and Xam Nua experience warm days and cold nights as the average temperatures register in the 10°C (50°F) to 21.1°C (70°F) range. Luang Prabang is relatively warm, with average temperatures between 17.8°C (64°F) and 28.9°C (84°F). Vientiane is dry and warm between 18.9°C (66°F) and 30°C (86°F). The far south sees daytime temperatures at 31.1°C (88°F). Precipitation is light or absent in most regions by November-end. The relative humidity drops in the range of 55% to 65% to make the conditions comfortable. A sweater is useful in the evenings, but the atmosphere generally does not warrant warm winter clothing. Expect the cold to increase with each passing day in November in Laos.
Weather in December
December is the beginning of the mild to cold winter in Laos. The atmosphere becomes pleasant due to the drop in humidity and temperatures. The average temperatures in Vientiane register in the mild 17.2°C (63°F) to 27.8°C (82°F) range, while Attapu is between 20°C (68°F) to 29.4°C (84.9°F). Luang Prabang has mild temperatures between 14.4°C (57.9°F) to 25.6°C (78.1°F). The days are warm, with ample sunshine. Nights are cold in the mountains. The daily sunshine lasts for 8 hours, and the ultraviolet index of the sun is at 8, the least of the year. December 21 is the shortest day in Vientiane, with 11 hours and 3 minutes of daylight. The daily average wind speeds are between 7.2km/h (4.5mph) to 8km/h (5mph) in the central-southern plains. Wind speeds in the mountains remain less than 4.8km/h (3mph). The northeast monsoon brings light rainfall, but tourists can mostly do without an umbrella. A jacket or sweater maintains warmth in the cold conditions. December offers excellent weather to visit Laos.