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I am now in my mid-late 40s and I grew up in the East Bay, in the foothills of Mt. Diablo. We relocated to my childhood home, where my parents had remained until recently. As a 1970s tract home, it still lacks air-conditioning and has relatively poor thermal efficiency, just as it did back then. This past week, we have tried to manage the house thermals as best as we can, venting at night and closing it up through the heat of the day. It has been tough with the humid and warm nights and consecutive hot days.

The temperature profile reminds me more of times in the tropics, though it is still comparatively dry here. We've managed roughly a 10F delta between the indoors and outdoors through the peak afternoon hours. The past few days when it got to 105-107 locally, it was around 95F indoors when the temperatures equalized and it was beneficial to open windows again in the evening. This morning, it only cooled to about 82F inside and has climbed back to 90F in 6 hours.

When I lived far away, I liked to reflect on the dark blue sky and desert-like temperature swings we sometimes had out here, with 100F+ days and nights below 60F. But, I cannot say that we never had hot weeks nor summer thunderstorms. I remember those too, along with other somewhat rare events like hard frosts, accumulating hail, or the occasional dusting of snow on local ridges and peaks.

So, with a longer view, I don't think this single event can be called a clear sign of climate change. Someone with a lot more statistical skills than me would need to model the frequency of events and trends and uncertainties...

My anecdote is the opposite. I lived in Santa Clara from 2002-2010, San Carlos 2010-2011, Belmont 2011-2014, Redwood City 2014-present.

Never had AC on the Peninsula. We have heatwaves every year. This summer has been remarkably mild, low 70s most of July and August until now. We got our heatwave. A bit more humid than normal thanks to tropical storm remnants, 70f dewpoint and 95f on Sunday, 65f dewpoint and spiked to 105f Saturday briefly.

It seems fractionally warmer than most heatwaves, and slightly longer, but doesn't 'feel' indicative of a trend.

Still no A/C, and I guess I notice it more now that I'm home 24/7, but still totally do-able.

Been running the house fan overnight to get the rooms down into the mid-high 70s.

That's contrary to my experience. I lived in south bay and the peninsula 2004-2010 and needed a/c every summer, for multiple weeks each year. For two of those years I didn't have a/c and had a lot of sleep loss those summers when daytime temperatures would break 90F, and occasionally 100F. Even when we'd "only" get mid-80F temperatures, I'd still want to run the a/c during the day if I was home. Feeling sticky while sitting on one's couch is no fun.

I've lived in SF since 2010, and there have been multiple weeks in the summer, during the past 5 or 6 years, where I've been unable to sleep due to heat. That sort of thing was rare in the 4 or 5 years prior. Just over this past weekend my inside temperature topped at just below 90F, with the outdoor daytime temperature getting as high as 98F. By the time I went to sleep, the indoor temperature was still in the low 80s, with windows open and fans on full.

If you don't require a/c at those temperatures in order to sleep well, lucky you, but then I wouldn't characterize you as typical.

Sorry, I had A/C when I lived in Santa Clara, that was poorly worded. I remember well the heat wave of 2006 where it peaked at 107 for 3 days in a row (and of course was over 100 for longer than that).

I think one major difference this year with the current heatwave is that everyone's working from home. They're not going to an air conditioned office to work during the day, or they don't have the ability to go to the local library or Starbucks to sit and work. It's much worse having to sit through a heat wave at home with no A/C this year than in previous years.

And being home you heat the place by existing, running things, and opening windows to the heat. If you leave a house locked, it heats up pretty slowly, and if you get back towards dark, it will cool off faster from a lower temperature.

It's just a really weird year all around.

I agree with you. I've lived in the Bay Area over 20 years now. Heat waves are nothing special, it happens every year. OP is completely overexaggerating. Overall, from Peninsula to SF, you can survive most days without AC, except for about one week a year where it sucks. This year sucks worse because everyone is stuck at home, instead of an air conditioned office, if you're lucky to work. It used to be the case that you would just stay at work late until it cooled off but that didn't happen this year.

Yes, it got hot on Friday and Saturday but those were the first two very hot days all year. This year has been overall pretty average, if not a bit cooler than average years.

Not my experience at all. I've lived in Marin county for 30 years, and this doesn't feel like anything extreme. I can recall many, many similar heat waves in my life. My bet is that the bay area has many micro-climates, and people's experiences can differ wildly. It's hard to extrapolate a trend from this kind of anecdota.

Edit: The summer rain/thunderstorm we had yesterday, now that is rare.

"There would be five or six wet and wonderful years when there might be nineteen to twenty-five inches of rain, and the land would shout with grass. Then would come six or seven pretty good years of twelve to sixteen inches of rain. And then the dry years would come, and sometimes there would be only seven or eight inches of rain... And it never failed that during the dry years the people forgot about the rich years, and during the wet years they lost all memory of the dry years. It was always that way."

Whenever Californians talk about whether I'm reminded of this Steinbeck quote.

East of Eden, the most convincing account of what if feels like to have lived in Northern/Central California, even if just for the description of the land. For those who haven't read it, please do. It's a tale that will never really leave you.

I live in Gilroy, and we've had 3 days of 105+ weather. When the house I live in was built, they put in a 3-ton unit, which was complete fine for the first 20 years my family lived here. I replaced it a few years ago with a 4-ton unit, and added extra blown-in insulation. It has barely kept up with the heatwave. Next is dual-pane windows, I guess. There are a lot of folks with less who are straight-out suffering. They re-opened the local library to function as a cooling center. Difficult to do during covid, but heatstroke is dangerous, too. Rough times.

Fancy insulation, double pane glass, etc are great for the heating season. They reduce conductive heat transfer, which is (roughly) proportional to the indoor-outdoor temperature difference. Even on a 100F day, the indoor-outdoor difference with A/C set to 75F is only 25F, which is equivalent to heating to 70F on a mild 45F winter day.

Try looking for major sources of solar heating instead. Windows and especially skylights are big culprits. So are inadequately insulated roof / ceiling assemblies.

You can put solar film on windows, use indoor or outdoor shades, or replace glass with low SHGC (solar heat gain coefficient) glass to reduce heating.

One unexpectedly strong benefit of the panels we put on our roof was the lower cooling bill, even before we were allowed to switch on the panels and use the power generated. Our roof geometry only allowed for a 65% solution instead of the 80% we were aiming for, and this unaccounted for improvement almost made the difference.

Going from a three to four ton unit was a mistake. One that's easy to make because it's counter-intuitive. And because bigger units are more expensive there's a sales incentive to sell bigger units too. To be effective at cooling people an air conditioner needs to remove latent heat in the form of water vapor. Lowering the air temperature isn't enough.

Oversized units short-cycle, lowering the air temperature significantly faster than they remove latent heat by condensing water vapor. The controlling thermostat turns the unit off quickly because the big unit quickly reduces the air temperature. The latent heat in the water vapor remains in the air. People still feel hot.

Basically, a residential air conditioner should be running most of the time if it's properly sized. Oversized units will come on, run for a few minutes, shut down for a few minutes, run for a few minutes, etc.

Double pane windows and blown insulation will magnify the effect because the air conditioner will reduce the air temperature more quickly and efficiently and leave more latent heat in the air.

Note that latent heat in the air from water vapor increases with temperature. That's why we talk in terms of relative humidity. So oversizing is less of an issue for heating season and double pane windows and extra insulation help.

I know you mean well, but I promise you, it wasn't a mistake. :) It's not rapid cycling, it's barely keeping up. It has literally gotten hotter here over the years. That's what I was trying to get at with my original post- what was appropriately-sized in decades past is no longer enough.

Don't some modern high-end residential HVAC systems have separate air conditioners and dehumidifiers to provide more granularity (and perhaps effectiveness or energy efficiency) between the two effects?

My understanding is modern compressor tech has already resolved that issue.

Wait - you don't even have dual-pane glass? That's like leaving a door ajar all day.

You can fake a second pane by putting plastic film over the window frame and taping it securely around the edges so there's no leakage, capturing the air between it and the glass. This will act as an insulating layer. Air leakage = heat transfer.

But you're better off replacing the windows with dual-pane units that have low-e coatings. Maybe the government or your utility has a program to help cover the replacement cost.

Yup. Currently have the plastic film deployed on about half my windows. It's obviously not true double-pane, but it makes a real difference. Well worth the $. For folks who don't know, once you've applied the plastic film, you shrink it with a hairdryer until it is smooth. If you take your time, it doesn't look bad at all, and is optically clear.

3M makes a variety of films for solar reduction and safety; they’re pretty great. Only available through certified installers but we had them done to protect our historic single pane windows, and while we were at it we had some UV film put on our large west-facing windows.

> For the first time in ten years

Had your coolant pressure checked lately? Heat exchanger fins clean, clear, and straight?

I haven't actually had it checked but I'm pretty sure that the A/C is working just fine. While it is running it produces plenty of cold air. And although it is almost ten years old, it hasn't seen a lot of use during that time. Until now, that is.

If your unit is too big it actually makes things worse, because it cycles on and off a lot more which in turn means it pulls less humidity out of the air. I think the rule is you want one ton per 600sq ft that you’re cooling, give or take.

I'm pretty sure that we're underpowered if anything. Our house is three stories, built into a hill. Only the top two floors are even plumbed for A/C and only the top floor has a compressor installed. Like I said earlier, the builder didn't think we'd need A/C at all.

Humidity inside is running about 50% at the moment.

> Humidity inside is running about 50% at the moment.

Drop that by 10-15% with a dehumidifier and you’ll feel a heck of a lot cooler despite temperature being the same.

Minisplits upstairs might be a good idea. Also, anything to reduce the stack effect. You might have air leaks pulling heat upwards all day. Our house is old and retrofitted, so the return air upstairs is inadequate but closing the downstairs vents makes a huge difference in the summer, since old air sinks.

> This Time It's Different

I'm on the other side of the planet in Northern Europe, and I feel the same. This summer has been very warm, it feels more like we are in some Mediterranean city (especially with all the outdoor seating due to COVID). We haven't had any record breaking highs, but the number of days when it has been 30c+ has been very unusual. Coupled with last winter which basically never came (usually we get -25c and frozen lakes; that never happened), we'll see what this year brings...

I've been here my entire life. This is pretty bad. In my 30 years i've definitely never experienced a hot summer thunderstorm like the other night. It feels very bizarre.

Same. Never before seen a thunderstorm where no precipitation hit the ground.

The heat doesn't feel so new to me. As a kid I was always watching for those 100F+ days with the fascination of hitting triple digits. I have 30+ years of seeing those.

The thunderstorm was crazy tho.

that thunderstorm WAS epic, best I've seen since I lived here. Had the windows open all night, it was wonderful. it rained pretty hard at times here (Redwood City)

The heatwave of 2006 was much worse than this, longer and hotter, but I admit there were no thunderstorms.

Just to add to this perspective. I live in Austin, TX, in April of this year it is hot enough outside that the A/C has to stay on constantly day and night. It's August and the A/C is never off. I don't expect the A/C to turn off until late October. That's 6 months of non-stop A/C in our apartment. That's insane to me.

That seems normal to me for Texas, though. Most population growth across TX, NM, AZ happened after the invention of air conditioning, precisely because it's uncomfortable there for half the year without it.

That is normal for Texas - but most buildings have central air so it’s not so bad. In NYC I’m in a pre-war building that has no A/C or ducting so I have to put in window units which only have a 3-5 year lifespan and aren’t horribly efficient , I can’t put in ceiling fans because the ceiling can’t support the weight (no cross beam or something), I’m limited in A/C size by the wiring, and until last year I had the old Edison S-type fuses which tend to blow in warm weather so you had to keep a shoe box of them around just in case - last year the super put in a breaker panel and man it has been wonderful, I’ve yet to even have to reset one of them.

It's always odd to hear people complain about California weather.

Just for the record, I'm not actually complaining about the weather. I still would not trade our weather for anyplace else in the world. But the trend over the ten years I've been living here full time (and some shorter-term stints living here in the 80's) seems alarming to me.

Part of the reason for that is because our houses are built for only temperate weather, especially the older ones.

My house was built in the 60s. It had single pane windows and no insulation under the floor in the crawlspace. It also had no attic fan.

We upgraded the windows and put in an attic fan, and that mostly works, but we still need the A/C a lot these last few years.

The house just doesn't hold temperature well. If there is more than a few degrees variance in either direction the temp swings wildly if I turn off the a/c.

This house was designed for the air outside to always be right around 72.

Another related story, I was using a datacenter in San Francisco. When the outside temp hit 85, we had to start shutting down servers. They told us the datacenter was designed with the assumption that the outside temp wouldn't ever get past 80.

No one in California is prepared for anything remotely close to actual weather, with the exception of people who live in the mountains. Thus any deviation from the extremely limited norm seems shocking.

That said, I grew up in southern ontario where discussing the weather is pretty much a widespread hobby, so it's actually kind of nice to have weather to discuss.

> my first-hand experience that This Time It's Different. I've lived on the SF peninsula for 10 years.

Wait, are you saying that your concern is based on a personal experience of 10 years in a place? Besides the fact that your observations might be down to pure chance, there are also strong decade and multi-decade local climate cycles.

This is not consistent with my experience; I've lived in the same peninsula home for 10 years and can recall multiple summers with waves this bad or worse.

Same here. Same place in SF for 10 years. It was pretty predictable to have anywhere from 7 days to 21 days of temperatures in 85-95F range. Some years it's less, others more.

This heatwave doesn't seem out of the norm.

for me it's been the opposite, it has been unnervingly moderate as far as North Texas summers go the past 5 summers at least. I really feel for the coastal refugees that have moved to the area once a hot summer shows up. ...3 or 4 consecutive > 100F weeks when the roads start to melt and random fires breaking out in grass everywhere, the wind blows and it just gets hotter etc...