When it falls and why it moves
Semana Santa does not fall on the same dates each year because it follows the moon: Easter Sunday is the first Sunday after the first full moon of spring, so the whole week drifts between late March and mid-April. In practice that matters little, because what stops in Mexico is not one week but two: Holy Week itself and the Easter week that follows it, which line up with the spring school holidays and with the leave half the country takes. It is the largest movement of people in the Mexican year.
It is worth grasping the scale before booking anything. This is not about foreign tourists, who are a minority in those weeks, but about Mexican families driving or taking the bus to the coast, to the grandparents' town or to the same place they go every year. The federal highways fill up on the Friday before Palm Sunday, long-distance coaches sell out weeks in advance, and beach hotels charge their highest rate of the year, well above what they ask in December. Anyone improvising across that fortnight pays double or sleeps badly.
The fortnight, day by day
The fortnight has a recognisable shape, and it helps to read it as a curve rather than a solid block. The movement begins on the Friday or Saturday before Palm Sunday, when the first cars leave, and builds towards Maundy Thursday and Good Friday, the two days of heaviest saturation anywhere in the country. By Holy Saturday and Easter Sunday people are settled wherever they wanted to be, and the return concentrates on Sunday afternoon and Monday, with slow roads heading back into the big cities. Nothing about that pattern changes from year to year.
The second week, Easter week, behaves differently. There are no processions or religious events left, but schools are still closed and plenty of families use exactly those days to travel more cheaply, so the beaches stay full while the cities begin to recover their rhythm. The real price spike is concentrated in the first week; in the second there is usually some slack, especially from Wednesday onwards. If the dates are negotiable, travelling the week after Easter Sunday gives you almost the same advantages with considerably fewer people on top of you.
Where the whole country goes
The default destination is the coast. Acapulco, Veracruz, Mazatlán, Puerto Vallarta, Cancún and virtually any beach reachable by road take in whole families who arrive with a cool box, a parasol and sometimes no reservation at all, willing to sleep wherever they can. The sand fills from early morning, the restaurants along the shore work at their limit, and the noise does not drop until well into the night. It is an enormously cheerful experience if you turn up expecting that, and a fairly disappointing one if what you wanted was a quiet beach at sunset.
The pueblos mágicos are the second magnet and they take the pressure worse, because they are small by definition. San Miguel de Allende, Taxco, Valle de Bravo, Tepoztlán and Pátzcuaro go from walkable streets to queues just to reach the centre, overflowing car parks and an hour's wait for a table. In the smaller towns the water supply and the public toilets run short, and the traffic on the approach can add two hours to the final stretch of the drive. If the calm of the place was the reason for going, this is precisely the fortnight to avoid.
The processions and the Iztapalapa Passion
What anyone who only looks at prices misses is that these two weeks hold the most extraordinary popular liturgy of the Mexican year. The Passion play staged in Iztapalapa, on the eastern edge of Mexico City, has been running for more than a century and a half and draws hundreds of thousands of people to the Cerro de la Estrella on Good Friday, with a cast made up entirely of local residents. It is not a show for tourists and was never conceived as one, and that is precisely why it is worth going.
Different regions produce very different versions of the same calendar. In Taxco the penitents come out carrying bundles of thorns and chains, in a night procession that is hard to watch and harder to perform. In San Luis Potosí the Procesión del Silencio crosses the centre without a single word, only a drum. In Oaxaca, Pátzcuaro or San Cristóbal the flower carpets and the images carried on shoulders occupy the streets for hours. All of this is free, happens in plain view of anyone, and usually demands nothing more than patience and a spot claimed early.
The half-empty cities
The other side of all this is that the big cities empty out. Mexico City loses a large share of its population over those days and becomes something it almost never is: a capital with free-flowing traffic, parking available in Roma and Condesa, tables without a reservation and noticeably cleaner air. Guadalajara, Monterrey, Puebla and Querétaro behave the same way. For a visitor from abroad who is not chasing a beach, it is the best week of the year to walk a historic centre without being jostled by anyone at all.
The price of that calm is that half the city is shut. Many family fondas pull the shutter down for the whole week, some museums close on Maundy Thursday and Good Friday, banks and offices do not open on those two days, and several municipalities apply a dry law for part of the period, so alcohol is not always on sale. Markets and neighbourhood taquerías usually keep working, and urban hotels drop their rates exactly when the coastal ones triple theirs. It pays to check opening hours on the day rather than trusting what the internet says.
The booking arithmetic
The practical rule is simple: the more rigid the seat, the sooner it sells out. First-class coaches towards the coast and towards the towns with processions usually go four to eight weeks ahead, and the departures on the Wednesday and Thursday before Good Friday are the first to disappear. Domestic flights hold on a little longer, but the fare climbs steadily and never comes back down. Beach hotels close out their sensible availability two or three months in advance, and what is left afterwards is either expensive or a long way from the water.
The other half of the arithmetic is deciding what you are buying. If the beach is the point, accept high-season pricing and book early, or shift the trip to the second week. If the processions are the point, the money goes on the transfer and on sleeping near the route, not on a luxury room. And if the point is simply to see Mexico, the most profitable move of all is to stay in a big city, pay low-season rates and leave the coast for another month of the year entirely.
What people always ask
Six questions that always come up when somebody realises their dates overlap with Mexican Holy Week. They run from the logistical to the thing nobody wants to hear, which is that no bargain exists on the coast during that fortnight, however hard you look. They are answered assuming the trip is already booked and the dates cannot move, which is the real situation of almost everyone who turns up asking. With room to choose, the short answer is always the same: shift a week later and sleep in a big city.
It is worth closing with an idea that does not fit into a short answer. Semana Santa is not an obstacle to be dodged but the best window of the year for seeing how the country works from the inside: neighbourhood liturgy, highways full of families, towns given over entirely to their own festival. The mistake is not travelling on these dates, it is travelling on these dates with the plan you would use in any other month. Adjust the plan and the fortnight becomes extraordinary, and in the big cities cheaper and easier too.