Do you need to know, when is the best time to go to Mexico? Then you should take a look here, what weather you can expect there during the year.
The climate of Mexico is varied, somewhere it is tropical, somewhere desert. In the north you can expect experiences lower temperatures during winter and less rains during the year. In the south the temperatures are quite constant year round. But you should alway consider the elevation of the place, where you are planning to go. Most of the country has a rainy season from June to October.
As Mexico has a really huge area, the information below relate mostly only to the area around the capital of this country. To see information about other places, please, choose one of these areas: Baja California, Bajío, Central Mexico, Northern Mexico, Pacific Coast, Yucatán Peninsula.
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 April, the average maximum temperature is 27.2 ℃ (80.96 ℉). The average minimum temperature in this month is 10.9 ℃ (51.62 ℉). The coldest month here is December, the average maximum temperature is 21.2 ℃ (70.16 ℉). The average minimum temperature in this month is 6.9 ℃ (44.42 ℉). The most rainy month here is July, the average number of rainy days is 23.6. The least rainy month here is February, the average number of rainy days is 2.1. 
When travelling to some places in Mexico, always consider the altitude of the the place as well. The highest point here is Volcan Pico de Orizaba (5636 m) and the lowest point is Laguna Salada (-10 m). So there are huge differences in altitudes in this country and the weather is very different in them therefore. 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 Mexico in January is this: The average highest temperature in Mexico in January is 21.5 ℃ (70.7 ℉). The average lowest temperature is 6.1 ℃ (42.98 ℉). At the beginning of January you can expect lower temperatures, the average highest temperature is around 21.35 ℃ (70.43 ℉). At the end of January you can expect higher temperatures, the average highest temperature is around 22.25 ℃ (72.05 ℉). The average number of rainy days in January is 2.3. The average rainfall is 11.2 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 10:58 (hours and minutes), in the middle of the month 11:05 and at the end of the month 11:16.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 Mexico in February is this: The average highest temperature in Mexico in February is 23 ℃ (73.4 ℉). The average lowest temperature is 7.3 ℃ (45.14 ℉). At the beginning of February you can expect lower temperatures, the average highest temperature is around 22.25 ℃ (72.05 ℉). At the end of February you can expect higher temperatures, the average highest temperature is around 24.25 ℃ (75.65 ℉). The average number of rainy days in February is 2.1. The average rainfall is 4.3 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 11:16 (hours and minutes), in the middle of the month 11:30 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 Mexico in March is this: The average highest temperature in Mexico in March is 25.5 ℃ (77.9 ℉). The average lowest temperature is 9.4 ℃ (48.92 ℉). At the beginning of March you can expect lower temperatures, the average highest temperature is around 24.25 ℃ (75.65 ℉). At the end of March you can expect higher temperatures, the average highest temperature is around 26.35 ℃ (79.43 ℉). The average number of rainy days in March is 3. The average rainfall is 10.3 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 11:45 (hours and minutes), in the middle of the month 12:02 and at the end of the month 12:19.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.Typical (usual) weather in Mexico in April is this: The average highest temperature in Mexico in April is 27.2 ℃ (80.96 ℉). The average lowest temperature is 10.9 ℃ (51.62 ℉). At the beginning of April you can expect lower temperatures, the average highest temperature is around 26.35 ℃ (79.43 ℉). At the end of April you can expect lower temperatures, the average highest temperature is around 26.7 ℃ (80.06 ℉). The average number of rainy days in April is 7.9. The average rainfall is 25.3 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 12:19 (hours and minutes), in the middle of the month 12:35 and at the end of the month 12:50.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 Mexico in May is this: The average highest temperature in Mexico in May is 26.2 ℃ (79.16 ℉). The average lowest temperature is 11.7 ℃ (53.06 ℉). At the beginning of May you can expect higher temperatures, the average highest temperature is around 26.7 ℃ (80.06 ℉). At the end of May you can expect lower temperatures, the average highest temperature is around 25.25 ℃ (77.45 ℉). The average number of rainy days in May is 12.4. The average rainfall is 55 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 12:50 (hours and minutes), in the middle of the month 13:02 and at the end of the month 13:12.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 Mexico in June is this: The average highest temperature in Mexico in June is 24.3 ℃ (75.74 ℉). The average lowest temperature is 12.3 ℃ (54.14 ℉). At the beginning of June you can expect higher temperatures, the average highest temperature is around 25.25 ℃ (77.45 ℉). At the end of June you can expect lower temperatures, the average highest temperature is around 23.6 ℃ (74.48 ℉). The average number of rainy days in June is 17.5. The average rainfall is 133.9 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 13:12 (hours and minutes), in the middle of the month 13:17 and at the end of the month 13:17.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 Mexico in July is this: The average highest temperature in Mexico in July is 22.9 ℃ (73.22 ℉). The average lowest temperature is 11.5 ℃ (52.7 ℉). At the beginning of July you can expect higher temperatures, the average highest temperature is around 23.6 ℃ (74.48 ℉). At the end of July you can expect higher temperatures, the average highest temperature is around 23.05 ℃ (73.49 ℉). The average number of rainy days in July is 23.6. The average rainfall is 171.2 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 13:17 (hours and minutes), in the middle of the month 13:12 and at the end of the month 13:02.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 Mexico in August is this: The average highest temperature in Mexico in August is 23.2 ℃ (73.76 ℉). The average lowest temperature is 11.9 ℃ (53.42 ℉). At the beginning of August you can expect lower temperatures, the average highest temperature is around 23.05 ℃ (73.49 ℉). At the end of August you can expect lower temperatures, the average highest temperature is around 22.6 ℃ (72.68 ℉). The average number of rainy days in August is 22.8. The average rainfall is 166.3 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 13:02 (hours and minutes), in the middle of the month 12:49 and at the end of the month 12:34.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 Mexico in September is this: The average highest temperature in Mexico in September is 22 ℃ (71.6 ℉). The average lowest temperature is 11.6 ℃ (52.88 ℉). At the beginning of September you can expect higher temperatures, the average highest temperature is around 22.6 ℃ (72.68 ℉). At the end of September you can expect higher temperatures, the average highest temperature is around 22.1 ℃ (71.78 ℉). The average number of rainy days in September is 18.9. The average rainfall is 143.6 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 12:34 (hours and minutes), in the middle of the month 12:18 and at the end of the month 12:02.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 Mexico in October is this: The average highest temperature in Mexico in October is 22.2 ℃ (71.96 ℉). The average lowest temperature is 9.9 ℃ (49.82 ℉). At the beginning of October you can expect lower temperatures, the average highest temperature is around 22.1 ℃ (71.78 ℉). At the end of October you can expect lower temperatures, the average highest temperature is around 22.1 ℃ (71.78 ℉). The average number of rainy days in October is 9.5. The average rainfall is 65.3 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 12:02 (hours and minutes), in the middle of the month 11:45 and at the end of the month 11:30.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 Mexico in November is this: The average highest temperature in Mexico in November is 22 ℃ (71.6 ℉). The average lowest temperature is 7.9 ℃ (46.22 ℉). At the beginning of November you can expect higher temperatures, the average highest temperature is around 22.1 ℃ (71.78 ℉). At the end of November you can expect lower temperatures, the average highest temperature is around 21.6 ℃ (70.88 ℉). The average number of rainy days in November is 4.5. The average rainfall is 12.2 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 11:30 (hours and minutes), in the middle of the month 11:16 and at the end of the month 11:05.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 Mexico in December is this: The average highest temperature in Mexico in December is 21.2 ℃ (70.16 ℉). The average lowest temperature is 6.9 ℃ (44.42 ℉). At the beginning of December you can expect higher temperatures, the average highest temperature is around 21.6 ℃ (70.88 ℉). At the end of December you can expect higher temperatures, the average highest temperature is around 21.35 ℃ (70.43 ℉). The average number of rainy days in December is 2.6. The average rainfall is 5.9 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 11:05 (hours and minutes), in the middle of the month 10:58 and at the end of the month 10:57.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.