Despite its deep southern latitude, Oaxaca’s elevation, cooling sea breezes, and summer rain showers moderate the heat of its plentiful sunshine. Most of the state, excepting the remote mountain summits, basks in the tropics, never feeling the bite of frost.
The seashore and coastal plain, including all of the Isthmus, is truly a land of endless summer. Winter days are typically warm and rainless, peaking at 82–88°F (28–31°C) and dropping to 65–75°F (18–24°C) by midnight.
Summers on the Oaxaca beaches are warmer and wetter. Mornings are usually bright and balmy, warming to around 90°F (32°C). Early afternoons, clouds often gather and bring short, sometimes heavy, cooling showers. Later, the sun reappears, drying the sidewalks and beaches and warming the breeze just in time to enjoy a dazzling Oaxaca puesta del sol (sunset).
Visitors to Oaxaca City experience similar but more temperate seasons. Midwinter days are typically mild to warm, usually peaking between 70 and 75°F (21–24°C). Expect cool but frost-free winter nights between 45 and 60°F (9–16°C). Oaxaca City summers are delightful, with afternoons typically in the mid- to upper 80s (28–32°C) and pleasant evenings in the mid-70s (24–26°C), perfect for strolling. May, before the rains, is usually the warmest, with June, July, and August highs being moderated by afternoon showers.
Visitors should take note that Oaxaca’s rainfall, like all of Mexico’s, is strongly seasonal. Most years, nearly all the rainfall accumulates during the summer and early fall. Rains taper off in October and November and don’t usually return until June. May, before the rains, is typically Mexico’s warmest month. Relief comes with the cooling summer showers.
Many trees, especially along the coast, respond to the winter–spring drought by losing their leaves by February. This might make a typical late winter–early spring Oaxaca landscape appear barren to the visitor in March even though the same area will be blooming with greenery by July or August. If you prefer lush, jungle verdure to be part of your Mexico experience, you’ll enjoy plenty if you visit during the seven months from July through January.
© Bruce Whipperman from Moon Oaxaca, 5th edition