Do you need to know, when is the best time to go to Cambodia? Then you should take a look here, what weather you can expect there during the year.
The climate of Cambodia is tropical, with rainy monsoon season from May to November, and dry season from December to April. There are only very little seasonal variations of temperature.
When speaking about the usual weather in this state, the information is relevant for example for these popular places: Angkor Archaeological Park, Anlong Veng, Banlung, Banteay Chhmar, Battambang, Bokor National Park, Cardamom and Elephant Mountains, Chi Phat, Chlong, Eastern Cambodia, Kampong Cham, Kampong Speu, Kampong Thom, Kampot, Kep, Koh Ker, Koh Kong, Koh Rong, Koh Rung Sanloem, Koh Russei, Kratie, Krek, Mekong Lowlands and Central Plains, North western Cambodia, Pailin, Phnom Penh, Poipet, Preah Vihear, Pursat, Samraong, Senmonorom, Siem Reap, Sihanoukville, Sisophon, Stung Treng, Tatai, Tonle Sap Lake, Virachey National Park.
Let's look now what weather you can expect in the area around the capital and in many other cities. The warmest month here is March, the average maximum temperature is 35.2 ℃ (95.36 ℉). The average minimum temperature in this month is 24.2 ℃ (75.56 ℉). The coldest month here is December, the average maximum temperature is 29.8 ℃ (85.64 ℉). The average minimum temperature in this month is 21.6 ℃ (70.88 ℉). The most rainy month here is October, the average number of rainy days is 23.8. The least rainy month here is February, the average number of rainy days is 2.4. 
When travelling to some places in Cambodia, always consider the altitude of the the place as well. The highest point here is Phnum Aoral (1810 m) and the lowest point is Gulf of Thailand (0 m). So the differences in altitudes in this country are not negligible and you should expect the weather to be different in places in different altitudes. Keep in mind, that the temperature usually decreases by 1.2 - 1.9 ℃ (2.2 - 3.5 ℉) per 200 m (656 ft), depending on the other conditions. (And we should add, that in the very special condition named thermal inversion even the temperature may be higher in higher altitudes.)
Typical (usual) weather in Cambodia in January is this: The average highest temperature in Cambodia in January is 31.2 ℃ (88.16 ℉). The average lowest temperature is 21.7 ℃ (71.06 ℉). At the beginning of January you can expect lower temperatures, the average highest temperature is around 30.5 ℃ (86.9 ℉). At the end of January you can expect higher temperatures, the average highest temperature is around 32.05 ℃ (89.69 ℉). The average number of rainy days in January is 2.8. The average rainfall is 25.6 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:27 (hours and minutes), in the middle of the month 11:31 and at the end of the month 11:37.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Cambodia in February is this: The average highest temperature in Cambodia in February is 32.9 ℃ (91.22 ℉). The average lowest temperature is 22.9 ℃ (73.22 ℉). At the beginning of February you can expect lower temperatures, the average highest temperature is around 32.05 ℃ (89.69 ℉). At the end of February you can expect higher temperatures, the average highest temperature is around 34.05 ℃ (93.29 ℉). The average number of rainy days in February is 2.4. The average rainfall is 11.7 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:37 (hours and minutes), in the middle of the month 11:45 and at the end of the month 11:54.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Cambodia in March is this: The average highest temperature in Cambodia in March is 35.2 ℃ (95.36 ℉). The average lowest temperature is 24.2 ℃ (75.56 ℉). At the beginning of March you can expect lower temperatures, the average highest temperature is around 34.05 ℃ (93.29 ℉). At the end of March you can expect lower temperatures, the average highest temperature is around 35.2 ℃ (95.36 ℉). The average number of rainy days in March is 5.2. The average rainfall is 59.4 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:54 (hours and minutes), in the middle of the month 12:04 and at the end of the month 12:13.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Cambodia in April is this: The average highest temperature in Cambodia in April is 35.2 ℃ (95.36 ℉). The average lowest temperature is 25.1 ℃ (77.18 ℉). At the beginning of April you can expect lower temperatures, the average highest temperature is around 35.2 ℃ (95.36 ℉). At the end of April you can expect lower temperatures, the average highest temperature is around 34.75 ℃ (94.55 ℉). The average number of rainy days in April is 8.6. The average rainfall is 101 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:13 (hours and minutes), in the middle of the month 12:23 and at the end of the month 12:31.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Cambodia in May is this: The average highest temperature in Cambodia in May is 34.3 ℃ (93.74 ℉). The average lowest temperature is 25.8 ℃ (78.44 ℉). At the beginning of May you can expect higher temperatures, the average highest temperature is around 34.75 ℃ (94.55 ℉). At the end of May you can expect lower temperatures, the average highest temperature is around 34.05 ℃ (93.29 ℉). The average number of rainy days in May is 16. The average rainfall is 110.3 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:31 (hours and minutes), in the middle of the month 12:39 and at the end of the month 12:44.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Cambodia in June is this: The average highest temperature in Cambodia in June is 33.8 ℃ (92.84 ℉). The average lowest temperature is 25.8 ℃ (78.44 ℉). At the beginning of June you can expect higher temperatures, the average highest temperature is around 34.05 ℃ (93.29 ℉). At the end of June you can expect lower temperatures, the average highest temperature is around 33.35 ℃ (92.03 ℉). The average number of rainy days in June is 16.3. The average rainfall is 180.4 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:44 (hours and minutes), in the middle of the month 12:47 and at the end of the month 12:47.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Cambodia in July is this: The average highest temperature in Cambodia in July is 32.9 ℃ (91.22 ℉). The average lowest temperature is 25 ℃ (77 ℉). At the beginning of July you can expect higher temperatures, the average highest temperature is around 33.35 ℃ (92.03 ℉). At the end of July you can expect lower temperatures, the average highest temperature is around 32.45 ℃ (90.41 ℉). The average number of rainy days in July is 19.4. The average rainfall is 191.4 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:47 (hours and minutes), in the middle of the month 12:44 and at the end of the month 12:38.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Cambodia in August is this: The average highest temperature in Cambodia in August is 32 ℃ (89.6 ℉). The average lowest temperature is 25.3 ℃ (77.54 ℉). At the beginning of August you can expect higher temperatures, the average highest temperature is around 32.45 ℃ (90.41 ℉). At the end of August you can expect higher temperatures, the average highest temperature is around 32.1 ℃ (89.78 ℉). The average number of rainy days in August is 21.3. The average rainfall is 172 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:38 (hours and minutes), in the middle of the month 12:31 and at the end of the month 12:22.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Cambodia in September is this: The average highest temperature in Cambodia in September is 32.2 ℃ (89.96 ℉). The average lowest temperature is 24 ℃ (75.2 ℉). At the beginning of September you can expect lower temperatures, the average highest temperature is around 32.1 ℃ (89.78 ℉). At the end of September you can expect lower temperatures, the average highest temperature is around 31.8 ℃ (89.24 ℉). The average number of rainy days in September is 19.7. The average rainfall is 250.2 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:22 (hours and minutes), in the middle of the month 12:13 and at the end of the month 12:04.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Cambodia in October is this: The average highest temperature in Cambodia in October is 31.4 ℃ (88.52 ℉). The average lowest temperature is 24 ℃ (75.2 ℉). At the beginning of October you can expect higher temperatures, the average highest temperature is around 31.8 ℃ (89.24 ℉). At the end of October you can expect lower temperatures, the average highest temperature is around 30.8 ℃ (87.44 ℉). The average number of rainy days in October is 23.8. The average rainfall is 316.3 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 12:04 (hours and minutes), in the middle of the month 11:54 and at the end of the month 11:45.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Cambodia in November is this: The average highest temperature in Cambodia in November is 30.2 ℃ (86.36 ℉). The average lowest temperature is 22.4 ℃ (72.32 ℉). At the beginning of November you can expect higher temperatures, the average highest temperature is around 30.8 ℃ (87.44 ℉). At the end of November you can expect lower temperatures, the average highest temperature is around 30 ℃ (86 ℉). The average number of rainy days in November is 11.8. The average rainfall is 136.6 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:45 (hours and minutes), in the middle of the month 11:37 and at the end of the month 11:31.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.Typical (usual) weather in Cambodia in December is this: The average highest temperature in Cambodia in December is 29.8 ℃ (85.64 ℉). The average lowest temperature is 21.6 ℃ (70.88 ℉). At the beginning of December you can expect higher temperatures, the average highest temperature is around 30 ℃ (86 ℉). At the end of December you can expect higher temperatures, the average highest temperature is around 30.5 ℃ (86.9 ℉). The average number of rainy days in December is 4.9. The average rainfall is 79.9 mm (look here, what this number means). When planning your travel, please, keep in mind, that actual weather may differ from these average values. The length of the day at the beginning of this month is approximately 11:31 (hours and minutes), in the middle of the month 11:27 and at the end of the month 11:26.These numbers above are valid primarily for the capital and the area around it. It is important to say, that the weather may differ significantly in different altitudes, especially in mountains.| Siem Reap | temperature: - | highest temperature: 31.2 ℃ (88.16 ℉) | lowest temperature: 20.6 ℃ (69.08 ℉) | rainfall: 10.3mm | rainy days: 2.9 |
| Phnom Penh Pochentong | temperature: - | highest temperature: 29.8 ℃ (85.64 ℉) | lowest temperature: 21.6 ℃ (70.88 ℉) | rainfall: 79.9mm | rainy days: 4.9 |