The most popular times to visit the city of Oaxaca [1] are Christmas–New Year’s, the Guelaguetza [2] (gay-lah-GET-zah) dance festival in July, and Día de los Muertos [2] (Day of the Dead) week, around November 1. Although the crowds are biggest and hotel prices are highest, these are the times when Oaxaca City is at its merriest and most colorful.
By contrast, beaches are at their most popular twice yearly: during the Christmas–New Year’s holiday and Semana Santa, the pre- Easter week. Droves of folks, both foreign and local, crowd restaurants and lodgings and push up hotel rates.
Weather-wise, it’s important to know that Oaxaca (and most of Mexico) has two sharply defined seasons: wet summer–fall and dry winter–spring.
People often say Oaxaca is too hot in the summer. This, however, isn’t necessarily the case. In fact, increased summer cloud cover and showers can actually create average daily temperatures in July, August, and September that are cooler than clear and very warm late April, May, and early June temperatures.
The other summer advantage is the vegetation. If you like lush, green landscapes, summer–fall may be your season. This is true especially in the highlands around Oaxaca City [1], where myriads of multicolored wildflowers decorate the roadsides and the clouds seem to billow into a 1,000-mile-high blue sky.
If you don’t mind crowds and want to experience lots of local color, go during one of Oaxaca’s festivals [3]. If, however, you shun crowds but like the sunny, temperate winter, January, a low-occupancy season, is a good bet, especially on the beach.
October, November and the first half of December are also good times to go (except possibly for the crowded, expensive high-holiday El Día de los Muertos week, around November 1 and 2). Hotel prices are cheapest, the landscape is lush and green, beaches are beautifully uncrowded, and it’s cooler and not so rainy as July, August, and September.
Links:
[1] http://www.moon.com/destinations/oaxaca/oaxaca-city
[2] http://www.moon.com/destinations/oaxaca/oaxaca-city/entertainment-and-events/festivals
[3] http://www.moon.com/destinations/oaxaca/background/festivals-and-events/fiestas