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Here Comes the Rain Again

This is a three-part update, subtitled “What the hell happened to June?”

So one thing about living in Mexico that is very different from the US (or Canada, or the UK): we don’t really have four seasons here.

That’s because the spring-summer-fall-winter progression is a phenomenon specific to temperate latitudes, and most of Mexico is sub-tropical or tropical. In Köppen-Geiger climate terms, the area where Jak and I live is Cwa, which translates to “monsoon-influenced humid sub-tropical with dry winters and hot summers”. Our climate has more in common with northeastern India than anyplace in the United States. And if I had to break it down into seasons, I’d call it three: long wet warm, short cool, and long dry hot.

But mostly people here just talk about the dry season and the rainy season, because the boundary from the former to the latter is stark: every June, there comes a certain day when the North American Monsoon whooshes in and instantly cools everything off.

The what now? you may be asking. Yes, North America has its own monsoon! It mostly affects Mexico, but it also produces most of the annual rainfall in Arizona and New Mexico. (And I have some bad news for folks in those states.)

The monsoon season here produces mostly overnight rains with intermittent daytime clouds and showers, and usually lasts until sometime in late October or early November. Then we get between two and three months of cooler temperatures, but almost never actually freezing. Meanwhile, the rains get slowly less frequent, until in spring they stop altogether, and everything starts heating up again … until early June and the next monsoon.

Or at least, that’s how it’s gone every year in recorded history before this one.

This is our tenth year living in the Lake Chapala area, and the annual temperatures have risen slowly but pretty steadily over that time. Here’s what they looked like in 2014, our first full year:

As you can see, our ‘summer’, in the sense of ‘hottest season’, ran from mid-March to early June; it’s over just as the temperate northern summer is getting started.

Now here’s last year’s temperature graph, 2022. (White space just means spottier recording; the colored parts are the important bits.)

Technically these readings are taken at the Guadalajara airport, about 40km away from us, and don’t quite reflect the particular microclimate here between the mountains and the lake. But it’s close, and the trend is the same: in the hottest part of 2014, the temperature was generally pleasant by nine or ten p.m. at the latest. In April and May of 2022, the ‘hot’ (29°C-35°C, or 84°F-95°F) part of the day lasted two to four hours longer, until midnight and beyond.

Mexican construction is all brick masonry, which means high thermal mass; houses here slowly absorb heat during the day and release it equally slowly overnight. This can work to moderate the internal temperature, especially if you close the windows in the late morning, then open them all up just after sunset to get a good cross-breeze going. Houses here don’t have air conditioning as a rule; in a year like 2014 it might get uncomfortably warm indoors for a couple hours in the late afternoon for a few weeks, but people would get by with fans — and as soon as the sun sets, things start to cool off fast.

But that whole system falls apart when the overnight temperatures don’t get cool enough for long enough to dissipate the day’s accumulated heat; in that case the temperature inside the building ratchets slightly higher with every cloudless sunny day, which during the last two months of the dry season is usually all but one or two of them. Eventually you get to the point where it’s hotter inside than outside, all day long. Welcome to 2022.

While the planet has been slowly heating up, I personally reached the stage of perimenopause where my body forgot how to regulate its own internal temperature, resulting in several years of hot flashes and night sweats. My basal body temperature actually reset itself one entire Celsius degree higher, from 36°C to 37°C, but I don’t think my hypothalamus got the memo. I used to be able to handle anything from 19°C to 28°C (66°F to 82°F) without significant distress; now my comfort zone is a precise 25°C, full stop.

With higher temps both internally and externally, the heat peak in 2022 left me in serious misery. For most of six or seven weeks, it was too hot for me to sleep except between about three and seven in the morning. I broke out in giant heat rashes, itchy and raw. Even Jak found it borderline intolerable, and he didn’t have the hormonal aspect to contend with. So we were in complete and instant agreement that it was time to revise the long-term major expense plan and move “air conditioning” up to the number-one spot.

That also required us to make the conversion to solar power earlier than planned, and the whole project — coming right on the heels of the drastic (and infuriating) cost overruns of The Interminable Kitchen Remodel — really put us on financial thin ice. I mean, we lowered our planned 2022 retirement contributions by several thousand dollars, and used our entire cash emergency fund, just to pull it off — putting me in a state of teeth-grinding anxiety, as our income sources are perpetually precarious. But last September we managed to get both the solar panels and the most important heat-pump mini splits purchased and installed: in our bedroom and the great room (kitchen/dining/living area, which is also helping to cool Jak’s office until we can get a separate unit).

This turned out to be one of the top ten best decisions I’ve ever made in my life. Because not only did the dollar tank against the peso over the next six months (even as local inflation continued rising, meaning that our money is worth something like 30% less now), but as of 2023 the local temperatures are no longer just creeping incrementally higher. No, the whole North American monsoon pattern has been altered in a historically unprecedented way.

So the average high for this area peaks at 31°C in late April, holds steady through May, and then starts falling again on the second of June, indicating the mean start date for the monsoon, historically speaking. Across the most recent nine years that make up my personal experience, the actual day has varied across the first and second weeks, but was never earlier than June 2nd, suggesting a recent trend of later start dates compared to the overall historical record.

This year, the entire first and second weeks of June came and went without a drop. And the third week, same. Finally, this past Monday night the 26th, with just four days left in the month, it rained.

Here’s what that delay did to the temperatures. First, here’s 2022, when the monsoon arrived on June 9th: you can see that both the low and the high temps across the year are on the high side compared to the averages, but not wildly out of bounds. Overall, it follows the historical curves.

And now, 2023. History clearly no longer applies.

You can see exactly where the monsoon hit, and how three rains in four days put us back down into the normal range. And no, I know everyone’s on about El Niño right now, but this is not because of El Niño. We’ve had lots of El Niño years, and it’s never caused anything remotely like this before.

This is global warming permanently altering major continental weather patterns, pure and simple.

Here’s what those temperatures look like in an hourly graph:

Ah yes, we qualify for ‘sweltering’ now, hooray.

Now, remember what I said about the heat-retaining properties of masonry construction? That two-plus weeks where the low never dropped below 20°C and the highs hovered at 36°C to 37°C — cumulatively, without air conditioning, that would have put us at 39°C or 40°C indoors in the late afternoon. At minimum. That’s like 102°F-104°F.

We would not have survived that. I honestly don’t know what we would have done, with ourselves or the cats, but it would have been a shitshow of misery and panic, most likely accompanied by a giant flushing sound from the vicinity of our bank account.

Instead we turned on the magic make-cool-air boxes, and all was well.

So, back to the North American Monsoon: it starts down here in central Mexico and runs along the Western Sierra Madres, and kinda gets this clockwise gyre going that normally starts bringing storms to Arizona and New Mexico around the beginning of July. Only since we were three weeks late, I’m betting they will be similarly late. Which probably means record-breaking heat waves there as well.

One important question for all of us who depend on this weather pattern is whether the tail end of the monsoon season will also be extended … or not. ‘Not’ is bad, because it means a dramatic lowering of the total annual water, which will have all kinds of negative repercussions. I am holding out hope that we’ll make up those three weeks on the back end, mostly because the IPCC climate modeling in 2021 already predictedhigh confidence in delayed onsets and demises” of the North American Monsoon, and “low agreement on a projected decrease of NAmerM precipitation”. But we really are in unknown territory now.

So yeah, of course the year of wildly unprecedented weather would be the year I finally managed to go all-in on a vegetable garden.

Garden travails coming up next in part two …

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