There are really two different areas of Mexico. One is the Sea of Cortez, where the air and water are not tropical in the winter. The other area is - depending on your standard of warmth - from Mazatlan or Puerto Vallarta south, where it's almost always tropically warm.
Air temperatures in the Sea of Cortez can be cool from mid-November until March or April. And it can get downright cold when a Norther roars down from the United States. However, since the Sea of Cortez pretty much runs north-south for more than 550 miles, there is great variation in the effect of Northers and the air temperature. When a Norther is blowing 40 knots and it's very chilly in Conception Bay, for instance, it might only be blowing 15 and be just perfect in La Paz. The exceptions to Sea of Cortez weather are Cabo and Mazatlan, both of which stay warm year round. Mazatlan is affected by only the strongest Northers, while Cabo is immune because of tall mountains. While there can be spells of cool and cold air temperatures in the Sea of Cortez as early as November, the water temperature normally stays quite warm as late as early December. Water temperature cools rapidly and dramatically, so forget swimming from La Paz north without a wetsuit until March or April.  The bottom line is that the best times to cruise the fabled Sea of Cortez are the spring and fall. Winter is too cool for those who enjoy water sports and are looking for a great tan. Summer is very, very warm in the Sea - in fact, August and September are hot as Hades - but some folks still love it.
South of Mazatlan or Puerto Vallarta, the air and water temperatures are pleasant year round. While some Northers blow down as far south as Mazatlan, they never invade the sheltered waters of Banderas Bay or the Gold Coast. However, if you like serious warmth in the dead of winter, there's nothing like getting as far south as Zihuatanejo. The skies almost always seem to be blue in Zihuatanejo town. |
