Acapulco weather, month by month, for an owner

What is the weather in Acapulco like through the year?

It is hot every month and dry for more than half of the year. The thirty-year normals for the city's observatory put every month's mean temperature between 26.6 °C and 29.2 °C, with an annual mean of 28.0 °C — and put the annual rainfall at 1,240.4 mm, of which 93 per cent falls between June and October.

That is the whole climate in two sentences, and the second one is the one that matters to a building. Temperature that moves by less than three degrees across a year is not a force a house has to be defended against; twelve hundred millimetres of water arriving in five months, and then not arriving at all for the other seven, is.

The figures below come from station 12002, Acapulco de Juárez (Obs), the National Meteorological Service observatory at three metres above sea level, on the 1991-2020 normal — thirty years of data in every column. It is the right station for this purpose precisely because it sits at sea level in the city rather than inland or on high ground, which is where the houses are.

Read the last column on its own and the shape of the year appears more clearly than in the millimetres. It rains on 70 days out of 365, which means the rain is not spread thin across a wet season: it is concentrated into a small number of heavy days, averaging more than seventeen millimetres on each day it falls at all. A house is not being asked to cope with drizzle.

When is the rainy season, and what does the rain do to a closed house?

The rainy season runs from June to October, and in a normal year those five months carry 1,155.2 of the year's 1,240.4 millimetres. What they do to a closed house depends almost entirely on drainage, because 61 of the year's 70 rainy days fall inside that window and each one delivers, on average, more water than the whole of February.

September is the heaviest month on the normal — 281.0 mm across 15.4 days of rain — and the extremes in the same series are larger than the averages suggest. The wettest single month the station recorded in those thirty years was September 2017 at 693.7 mm, and the wettest single day was 207.8 mm on 20 June 2011: more than two hundred millimetres between one morning and the next. Nothing about a roof, a terrace or a run of guttering is tested by a normal. It is tested by that day.

What rain of that intensity finds is not usually a hole. It finds a joint that opened by a millimetre during the dry months, a drain with six months of leaves in it, a terrace outlet sized for average rainfall, a parapet flashing that lifted, a downpipe that discharges against a wall instead of away from it. Water on this coast arrives fast and leaves fast, and the damage is done in the minutes when it cannot get away — which is why the failures show up as staining on an internal wall rather than as a puddle anybody sees.

Ground slope compounds it. Much of the built coast here sits on hillside, so a house receives not only the rain that falls on it but a share of what falls above it, and a blocked channel upslope becomes somebody else's problem within one storm. The work of keeping that path clear before the season rather than after it is the plain content of preventive maintenance, and it is scheduled work rather than a response to anything.

It is worth saying plainly that this is a Pacific calendar and not a Caribbean one, because owners with houses on both coasts routinely apply the wrong dates. In the north-eastern Pacific the cyclone season runs from 15 May to 30 November, while in the Atlantic, which includes the Gulf of Mexico and the Caribbean, it runs from 1 June to 30 November — so hurricane season in Cancún opens more than two weeks later than the one here.

The peaks differ as well. The eastern Pacific season peaks in late August, with most systems between late June and early October; the Atlantic peaks on 10 September, with most activity from mid-August to mid-October. Two houses, two coasts, two sets of dates on which the same preparation has to already be finished — which is one of the reasons the work is described one place at a time rather than as a single national calendar, and why the Caribbean pages do not simply repeat this one.

What is the driest stretch, and why does it matter for paint and ironwork?

The dry stretch runs from December to April, and it is drier than almost anyone expects: those five months together carry a normal 25.8 mm, with April at 0.2 mm and a normal 0.2 days of rain in the entire month. It matters because it is the only window in the year in which paint, sealant, render and ironwork can be prepared, applied and left with any confidence that they will cure dry and stay dry.

Every exterior coating has two enemies on this coast and they arrive in opposite halves of the year. Moisture is the one everyone names: a surface that is damp when it is coated, or wetted before it has cured, fails from underneath regardless of what was written on the tin. Salt is the one that is forgotten, because it does not look like weather — it arrives on the air continuously, settles on everything facing the sea, and turns any coating applied over it into a film with a layer of crystals underneath.

So the dry season is not merely the convenient time to do exterior work. It is the only time the work can be done properly, and the difference between a house painted in February and the same house painted in September is measured in years rather than in appearance. The same is true of ironwork — gates, railings, window frames, shutter hardware, pool ladders, anything galvanised or painted — where the sequence is always the same: cut back to sound metal, wash the salt off, prime, coat, and finish before the first rain.

This is also why exterior work on a coastal house is planned rather than requested. A December-to-April window is four months wide, it comes once a year, and the decisions that fill it — which elevation this year, which ironwork, which sealant runs — are the substance of an annual plan agreed before the window opens rather than quotations sought after it has closed.

One further consequence of a dry season this dry is that the building itself moves. Timber shrinks, joints open, render crazes, and mortar dries out — and none of that is visible while it is happening, because nothing is being pushed through the gaps. The opening happens between December and May; the leak happens in June, in the same place, every year, until somebody closes it in the four months when closing it is possible.

What is the weather in Acapulco in December and January?

Acapulco weather in December is warm, bright and effectively rainless: the normals give 31.9 °C by day and 22.5 °C at night, with 7.8 mm of rain across 2.6 days. Acapulco weather in January is drier still — 31.4 °C and 21.9 °C, with 7.2 mm and 0.9 days of rain in the whole month.

These are the two months in which an absent owner is most likely to actually be in the house, and that coincidence is worth naming, because it decides what the visit is. Arriving in December means arriving six to eight weeks after the last serious rain — long enough for everything the wet season did to have finished doing it, dried, and settled into whatever state it is going to stay in until June.

That is the good news and the bad news in one sentence. A December arrival is comfortable, and it is also the moment at which a stain that appeared in September has had three months to spread quietly behind furniture, a damp patch has gone through one full drying cycle and left its edge on the plaster, and a corroded hinge has stopped being a hinge. None of it is dramatic in December. All of it started in September.

It is worth adding, because the search results will not, that cool here is a relative term. The coldest daily minimum the observatory recorded in any January across thirty years was 14.0 °C, on 21 January 1996, and the normal January minimum is 21.9 °C. A house on this coast is never cold, is never heated, and never gets the long freezing spell that dries a northern building out from the inside once a year.

What does humidity do to a house nobody opens for weeks?

It does what water does, only slower and out of sight: warm still air holds moisture against plaster, timber, textiles, leather and metal, and in a closed house nothing moves it along. The threshold is short — the US Environmental Protection Agency's guidance is that materials dried within 24 to 48 hours will in most cases not grow mould — and a building nobody enters for six weeks cannot meet it on its own.

The same guidance sets the target for the air itself: keep indoor humidity below 60 per cent relative humidity, ideally between 30 and 50. A coastal house shut through September holds nothing near that unless something is running — ventilation on a timer, a dehumidifier with a drain, air conditioning set to a maintenance temperature rather than off — and the honest way to state the local figure is not to state it: the station's normals publish temperature, rainfall and days with rain, and they do not publish relative humidity, so what follows is the mechanism rather than a number for this city.

The mechanism reaches the soft things first, because they hold the most water and complain the least. Mattresses, upholstery, curtains, rugs, anything stored in a closed wardrobe, anything leather, anything paper. Then it reaches the surfaces that stay coolest — the shaded side of an external wall, the back of a fitted cupboard, the underside of a stone counter — where warm damp air condenses without anyone having spilt anything.

Then it reaches the mechanical things, which is where the cost is. Hinges, locks, window hardware and shutter fittings corrode in place; electrical contacts, pumps and pool equipment corrode while switched off; and anything with a seal — a fridge door, a gasket, a shower tray — sits shut for two months in air that is working on it. A house closed with everything switched off at the board is not being protected. It is being left.

This is the part of the year that decides how much of the standing work of an administration office is real work rather than presence, and it is the part an owner abroad cannot see. What that work actually consists of, act by act, is set out in what a property manager does, day by day, and whether it is worth arranging at all for a house that earns nothing is weighed in is property management worth it.

What should be checked before and after the wet months?

Two visits, timed by the calendar rather than by anybody's arrival: one in May before the rain begins, and one in November after it has finished. The first is about keeping water out, the second is about finding where it got in, and neither of them is the visit made the day before an owner lands.

The May visit is drainage, and almost nothing else. Roof surfaces and parapets, every gutter and channel cleared to bare metal or bare concrete, every downpipe run with a hose until it discharges where it is supposed to, terrace and balcony outlets tested rather than looked at, flashings and sealant runs checked along their whole length, and the slope above the house walked to the boundary. Then the mechanical half: pump and gate motors serviced, storm shutters closed and reopened once to prove they still do, vegetation cut back from walls and roofs, and anything stored at floor level lifted off the floor.

The November visit is the same list read backwards, and it is the one that produces information. Where is the staining that was not there in May, and which elevation is it on. Which sealant joint moved. What is the reading behind the furniture that stood against the north wall all season. Which hinge, lock and contact has bloomed. What is the state of the pool equipment after four months of humid air and rain dilution. What has to be scheduled into the December-to-April window, which by then is six weeks away.

Between the two, the standing work is smaller and duller: get inside the house often enough that the air moves and somebody smells damp before it becomes a ceiling, keep whatever is running actually running, and photograph what is found rather than describing it later. A house does not deteriorate on a schedule anybody set. It deteriorates in the interval between the thing happening and somebody noticing.

All of which is only useful to an owner two thousand miles away if it arrives in a form they can check without asking for it — dated, itemised, with the photographs attached and the spending against them. That is what the monthly owner statement exists to be, and for a house on this coast the months that matter most in it are the five in the middle of the year. What the rest of the work looks like in this particular city, house type by house type, is set out on the page for Acapulco.