Pogoda Park Narodowy Tulum — grudzień

Regulars describe genuine trip-to-trip variance - one visitor's own account of ten December trips with rain only once for 20 minutes, another reporting rain 6 of 8 days, often a brief morning shower around 7am - with a cold front typically passing through about a week before Christmas named as the real wildcard. Our row backs that warm, still-showery read, 27C over 23.2C nights, with 63.7mm of rain across 14.1 days and humidity at 78 percent. Regulars are consistent a sweater or fleece belongs in the bag for evenings regardless of how warm the days run, temperatures dropping noticeably once that pre-Christmas front moves through. The sea sits at a warm 27.7C. The record: 9.5 hours of sun, an 18.1 kph wind and one of the cleanest air readings in this project, AQI 28.

May is the wrong half of the sargassum year here and the board does not soften it: through May and June the seaweed is everywhere, and the only honest way to plan is to treat the beach as a bonus rather than the reason for coming. Their answer is to go inland - the cenotes, the ruins, Sian Ka'an - and it is a good one. The heat is the other thing to know: 29.8C reads as 34C at 77.8 percent humidity, and the nights barely help at 25.9C feeling like 29C. The sea is 28.8C, warmer than the air after dark. Rain has started, 69.7mm across 12.6 days, mostly in the afternoon. A 20.1 kph wind is the only relief. The record: 11.6 hours of sun and AQI 37.

Tulum-forum threads on January sargassum are reassuring but not absolute: the season proper doesn't really start until February, so January typically sees little to none, and even the rare small patch that washes ashore isn't described as enough to ruin a trip. That said, posters are honest that a few January and February trips have been hit anyway - some days nothing, other days a real amount, entirely dependent on which way the wind and current are pushing that week, so nothing is truly guaranteed. Weather itself gets an easy write-up: warm, low-rain days and a sea that stays pleasantly warm from January through March, comfortable for long stretches in the water. The record: 26.4C days feeling like 28C, 22.4C nights, 53mm across 13.1 days, a 26.9C sea, 76 percent humidity and 9.5 hours of sun.

April in Tulum is the good weather and the start of the bad seaweed. The forum's sargassum season is April through October, and their honest position is that you should expect it anywhere on this coast in those months, that it can be genuinely bad, and that it changes within days - one account has a few clear beautiful days, several acceptable ones, then heavy weed and water full of it for the last four or five - because it moves with Atlantic storms, wind and tide. Two other April facts: Semana Santa falls mid-month and is one of the two busiest Mexican holiday periods, the first week worst, and this is still the tail of the expensive December-to-April season. Our row is the easy part, 28.5mm across 6.8 days. The record: 29.1C days that feel like 33C, 24.9C nights and a 27.8C sea.

February is the end of Tulum's clean-beach window and the forum explains it by wind direction rather than calendar. Through the winter the wind comes off the Gulf from the north, which keeps sargassum away; around February and March it swings east or southeast and starts bringing it in. So late February is when the first light amounts usually show, not every day and not much - the heavy months are April through October. Regulars are careful not to promise: most Novembers to Februaries are clear, some January and February trips have been caught anyway, and a storm in the Atlantic can change a week. The record: 27.2C days, 23.2C nights, 7.8 precipitation days, 10 hours of sun, a 26.9C sea and a 21 kph wind.