Do you need to know, when is the best time to go to El Salvador? Then you should take a look here, what weather you can expect there during the year.
The climate of El Salvador is tropical. The rainy season is from May to October, the dry season is from November to April. You can expect tropical weather on coast, but temperate weather in uplands.
When speaking about the usual weather in this state, the information is relevant for example for these popular places: Alegría, Apaneca, Berlín, Chalatenango, Eastern El Salvador, El Cuco, El Pital, El Tunco, Juayúa, La Libertad, La Unión, Morazán, San Francisco Gotera, San Luis del Carmen, San Miguel, San Salvador, Santa Ana, Santa Rosa de Lima, Santa Tecla, Sonsonate, Suchitoto, Western El Salvador.
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 32.7 ℃ (90.86 ℉). The average minimum temperature in this month is 18 ℃ (64.4 ℉). The coldest month here is October, the average maximum temperature is 29.1 ℃ (84.38 ℉). The average minimum temperature in this month is 18.8 ℃ (65.84 ℉). 
When travelling to some places in El Salvador, always consider the altitude of the the place as well. The highest point here is Cerro El Pital (2730 m) and the lowest point is Pacific Ocean (0 m). So there are quite big differences in altitudes in this country, so you can expect the weather to be different in different altitudes as well. 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 El Salvador in January is this: The average highest temperature in El Salvador in January is 30.5 ℃ (86.9 ℉). The average lowest temperature is 16.2 ℃ (61.16 ℉). At the beginning of January you can expect lower temperatures, the average highest temperature is around 30.15 ℃ (86.27 ℉). At the end of January you can expect lower temperatures, the average highest temperature is around 30.45 ℃ (86.81 ℉). The average rainfall is 4.9 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 11:19 (hours and minutes), in the middle of the month 11:24 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 El Salvador in February is this: The average highest temperature in El Salvador in February is 30.4 ℃ (86.72 ℉). The average lowest temperature is 16.7 ℃ (62.06 ℉). At the beginning of February you can expect higher temperatures, the average highest temperature is around 30.45 ℃ (86.81 ℉). At the end of February you can expect higher temperatures, the average highest temperature is around 31.55 ℃ (88.79 ℉). The average rainfall is 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 11:31 (hours and minutes), in the middle of the month 11:41 and at the end of the month 11:52.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 El Salvador in March is this: The average highest temperature in El Salvador in March is 32.7 ℃ (90.86 ℉). The average lowest temperature is 18 ℃ (64.4 ℉). At the beginning of March you can expect lower temperatures, the average highest temperature is around 31.55 ℃ (88.79 ℉). At the end of March you can expect lower temperatures, the average highest temperature is around 32.45 ℃ (90.41 ℉). The average rainfall is 9.2 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 11:52 (hours and minutes), in the middle of the month 12:03 and at the end of the month 12:15.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 El Salvador in April is this: The average highest temperature in El Salvador in April is 32.2 ℃ (89.96 ℉). The average lowest temperature is 19.2 ℃ (66.56 ℉). At the beginning of April you can expect higher temperatures, the average highest temperature is around 32.45 ℃ (90.41 ℉). At the end of April you can expect lower temperatures, the average highest temperature is around 31.45 ℃ (88.61 ℉). The average rainfall is 36.6 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 12:15 (hours and minutes), in the middle of the month 12:26 and at the end of the month 12:36.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 El Salvador in May is this: The average highest temperature in El Salvador in May is 30.7 ℃ (87.26 ℉). The average lowest temperature is 19.8 ℃ (67.64 ℉). At the beginning of May you can expect higher temperatures, the average highest temperature is around 31.45 ℃ (88.61 ℉). At the end of May you can expect lower temperatures, the average highest temperature is around 30.15 ℃ (86.27 ℉). The average rainfall is 155.4 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 12:36 (hours and minutes), in the middle of the month 12:45 and at the end of the month 12:52.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 El Salvador in June is this: The average highest temperature in El Salvador in June is 29.6 ℃ (85.28 ℉). The average lowest temperature is 19.4 ℃ (66.92 ℉). At the beginning of June you can expect higher temperatures, the average highest temperature is around 30.15 ℃ (86.27 ℉). At the end of June you can expect higher temperatures, the average highest temperature is around 29.65 ℃ (85.37 ℉). The average rainfall is 291.7 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 12:52 (hours and minutes), in the middle of the month 12:55 and at the end of the month 12:55.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 El Salvador in July is this: The average highest temperature in El Salvador in July is 29.7 ℃ (85.46 ℉). The average lowest temperature is 19.1 ℃ (66.38 ℉). At the beginning of July you can expect lower temperatures, the average highest temperature is around 29.65 ℃ (85.37 ℉). At the end of July you can expect higher temperatures, the average highest temperature is around 29.8 ℃ (85.64 ℉). The average rainfall is 310.6 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 12:55 (hours and minutes), in the middle of the month 12:51 and at the end of the month 12:45.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 El Salvador in August is this: The average highest temperature in El Salvador in August is 29.9 ℃ (85.82 ℉). The average lowest temperature is 19.5 ℃ (67.1 ℉). At the beginning of August you can expect lower temperatures, the average highest temperature is around 29.8 ℃ (85.64 ℉). At the end of August you can expect lower temperatures, the average highest temperature is around 29.75 ℃ (85.55 ℉). The average rainfall is 310.1 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 12:45 (hours and minutes), in the middle of the month 12:36 and at the end of the month 12:26.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.Typical (usual) weather in El Salvador in September is this: The average highest temperature in El Salvador in September is 29.6 ℃ (85.28 ℉). The average lowest temperature is 20 ℃ (68 ℉). At the beginning of September you can expect higher temperatures, the average highest temperature is around 29.75 ℃ (85.55 ℉). At the end of September you can expect lower temperatures, the average highest temperature is around 29.35 ℃ (84.83 ℉). The average rainfall is 344.3 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 12:26 (hours and minutes), in the middle of the month 12:14 and at the end of the month 12:03.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 El Salvador in October is this: The average highest temperature in El Salvador in October is 29.1 ℃ (84.38 ℉). The average lowest temperature is 18.8 ℃ (65.84 ℉). At the beginning of October you can expect higher temperatures, the average highest temperature is around 29.35 ℃ (84.83 ℉). At the end of October you can expect higher temperatures, the average highest temperature is around 29.3 ℃ (84.74 ℉). The average rainfall is 217.3 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 12:03 (hours and minutes), in the middle of the month 11:52 and at the end of the month 11:41.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 El Salvador in November is this: The average highest temperature in El Salvador in November is 29.5 ℃ (85.1 ℉). The average lowest temperature is 18.4 ℃ (65.12 ℉). At the beginning of November you can expect lower temperatures, the average highest temperature is around 29.3 ℃ (84.74 ℉). At the end of November you can expect higher temperatures, the average highest temperature is around 29.65 ℃ (85.37 ℉). The average rainfall is 35.9 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 11:41 (hours and minutes), in the middle of the month 11:31 and at the end of the month 11:24.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 El Salvador in December is this: The average highest temperature in El Salvador in December is 29.8 ℃ (85.64 ℉). The average lowest temperature is 16.7 ℃ (62.06 ℉). At the beginning of December you can expect lower temperatures, the average highest temperature is around 29.65 ℃ (85.37 ℉). At the end of December you can expect higher temperatures, the average highest temperature is around 30.15 ℃ (86.27 ℉). The average rainfall is 10.1 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 11:24 (hours and minutes), in the middle of the month 11:19 and at the end of the month 11:19.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.