Mexico's coasts tested: Caribbean or Pacific – and which Pacific?

Start with the month already available to you

JAN–APR  → all four are strong; water temperature and trip style decide
JUN–JUL  → Los Cabos stays dry while Puerto Vallarta's rain curve rises
AUG–SEP  → warm sea everywhere; the largest climate compromises
NOV–DEC  → broad recovery, especially clear in Puerto Vallarta

This is a map of historical monthly averages, not a ranking of beaches and not a forecast for a particular booking.

January to April: the rare four-way window

All four perform well in late winter and early spring, for different reasons. Cancún scores 89 in February and 88 in March; Tulum reaches 85–87 from January through March. Four to six rainy days and average highs around 26–30 °C create a relatively balanced Caribbean window.

Puerto Vallarta reaches 92 in February and 86 in March. March has no rainy day at the threshold used by the dataset, although the sea, at roughly 24 °C, is cooler than the Caribbean. Los Cabos scores 92–93 from January to April with zero or one rainy day, but its sea falls to about 21.8 °C in March.

The useful choice is therefore not “Mexico or Mexico”. It is warmer winter water in the Caribbean, Puerto Vallarta's very dry overall balance, or Los Cabos' dry air-and-land profile with the clearest gap between warm days and cooler water.

Summer splits the Pacific coast in two

“Pacific” is still too broad. Puerto Vallarta moves from one rainy day in May to eight in June and 15–16 in July and August. Monthly precipitation rises from 12 mm in May to 285 in July and 307 in August. The sea remains inviting and peaks near 30.2 °C in August.

Los Cabos behaves differently. July averages about two rainy days and 16 mm; August four days and 60 mm. Its trade-off is heat rather than Puerto Vallarta's rain frequency. The average daily high is about 30.8 °C in August and remains close to 30 °C through October. Travellers who value dry days over moderate walking temperatures will read this differently from those planning long outdoor days.

Combining the two Pacific destinations into one summer recommendation would hide the most useful distinction in the data.

Caribbean paradox: better water, weaker overall comfort

Cancún and Tulum reach their warmest sea values in August and September, around 29.2–29.5 °C. At the same time their overall scores fall: Cancún to 70 and 69, Tulum to 70 and 67. Hotter days, high humidity and more rain offset the water advantage.

October averages about 11 rainy days and 198 mm in Cancún, 12 days and 187 mm in Tulum. The sea is still around 29 °C. A beach-only metric would overrate the month; a rain-only warning would erase its warm-water appeal. Both facts belong in the decision.

Four profiles instead of one winner

What still needs a live check

Monthly climate cannot answer questions about a specific tropical storm, sargassum, surf or a temporary road closure. Those require current local information. Conditions also vary within each coastal region. The long-term series serves a different purpose: it prevents “Mexico in August” – or even “the Pacific coast in August” – from being treated as one climate.

Data basis: NASA POWER for land climate, NOAA OISST v2.1 for sea temperatures, and the official SMN/CONAGUA and INEGI climatology products for regional plausibility checks. Reference period 1991–2025; historical monthly averages, not a weather forecast.