The climate of Mexico is highly varied. The Tropic of Cancer effectively divides the country into temperate and tropical zones. Land north of the 24th parallel experiences cooler temperatures during the winter months. South of the 24th parallel, temperatures are fairly constant year round and vary solely as a function of elevation. The north of the country generally receives less precipitation than the south.
Areas south of the 24th parallel with elevations up to 1,000 meters (3,281 ft) such as the southern parts of both coastal plains as well as the Yucatán Peninsula, have a yearly median temperature between 24 and 28 °C (75.2 and 82.4 °F). Temperatures here remain high throughout the year, with only a 5 °C (9 °F) difference between winter and summer median temperatures. Although low-lying areas north of the 24th parallel are hot and humid during the summer, they generally have lower yearly temperature averages (from 20 to 24 °C or 68.0 to 75.2 °F) because of more moderate conditions during the winter
Regional weather forecasts and history for most areas of Mexico are available from Weather Underground and a good site for comparing different areas is WeatherSpark. From the perspective of moving to Mexico, you should consider year round conditions for any area you choose, as temperatures and rainfall can vary widely, particularly in coastal regions. What seems like the perfect spot while on vacation can turn unbearably hot and humid in the off-season and be subject to hurricane activity.