if the room is hot all the fan is gonna do is blow hot air

No, it would not work.

Physics explanation:

Short explanation:

Thank you Fuxx. I will try to find the coolest room in the house in order to store it in.

I recommend using a thermometer to inspect the temperature instead of relying solely on your human perception. Underground places like a basement work well.

Our basement is incredibly humid since it's mostly sealed shut until we need to use it. Not an ideal environment for an instrument.

is "detuning quite a bit" occurring while you play it, or in between playing when it sets idle? if the latter, this can be fairly normal and caused by a number of things. strings in the first hour of playing especially, and up to probably the first 10 hours of playing are more likely to detune. the position in which the guitar sits idly can shift the focus of its string tension to something that the guitar was not optimized for, which can detune it.

the more serious concern here is "is my guitar warping due to changes in temperature/humidity"? a detuned guitar simply requires tuning to remedy, but a warped neck will require a more serious 'tune-up' or 'set-up' from someone's who fiddled with a truss rod for a few years+.

if it seems your guitar is excessively detuning, it could be a number of other non-temperature related problems. and even if it is temperature related, it is something worth worrying about? temperature and humidity are a huge pain in the arse for guitar techs on massive tours with quickly changing environments, but those main issues (of wood warping) manifest in intonation and uneven action problems. ... to get to the tldr of my train of thought, how is this interfering with your playing of it? is it?
(more info would be helpful for a diagnosis)

why does it matter, do you not tune your guitar every time you grab it to play?

are you not keeping it in a case? If not you should.

its really bad to leave it in a hot room, it could cause the truss rod to become bent and your nice guitar will be ruined forever. Just try and leave it in the coolest room you have and no where near a radiator/heat source.

it matters because the wood can eventually crack or warp irreparably if the temp/humidity is too high.

maybe consider getting a humidifer like this one to keep the humidity inside your guitar constant? changing humidity can be dangerous to an instrument afaik

put a bowl of ice water infront of the fan

Get a case and a humidifier if you don't have them already. Normal temperatures shouldn't damage instruments but poor humidity in their storage areas will. If temperature is really a big issue just keep it in the coolest area in your house out of the sun.

Just don't let the guitar close to any window/radiator
tune it every time during summer

youll want to keep it at least 37% humidity, preferably between 40-60%. Too low and itll crack, too high and it will bend the wood in bad ways. Plus it also sounds pretty dull when in high humidity. Want to keep it in around room temperature too

Easiest way is to keep it in the case & get a cheap humidifier which is just some plastic u put between the strings and has a sponge in it. Wet sponge every couple of days and youre golden. if too humid youll need a dehumidifier

you should get a little temp/humidity monitor, theyre like under $20.

Keep it in a case silly

https://cdn.discordapp.com/attachments/315075100842131456/479411288880054312/fridge-clipart-1.png

Keep it in metalworks mid

I'm curious what make and modal of acoustic guitar you have. I used to work with a rare guitar dealer, and I've had the honor and privilege of working on some very expensive, rare, and exclusive pieces. Humidity and shifting barometric pressures can play a huge role in the detuning of acoustic guitars. If you do not leave your instruments in a controlled environment, its advised that you keep it in the case after you are done playing. It could also be many other factors, like your truss rode might need adjusting, if you leave it leaning against a wall, that will detune it. Is your guitar all original parts? What gauge strings do you use and do you switch between different gauge strings often?

All of these things and more play a factor, and sometimes older guitars just don't like to stay in tune. I work with mostly Gibson and Martins from the 30s-60s, and all of the tuning mechanism are typically very valuable and really bad (IMHO). Some people like janky guitars, kind of like gun nuts who think the m1 grand or the mosin-nagant is the end-all-be-all of war fighting guns, even today. One case of cost to maintain being more then probably the value of a instrument is Trigger, the guitar of Willie Nelson.

that doesn't make any sense, that would be the case only if the string got more tense to the point of damaging/curving the neck
if we are talking humidity then yes it affects the instrument, but the strings being detuned has nothing to do with damage

if you are concerned about warm environments damaging your guitar you shouldn't worry, i would however make sure that the instrument has a fresh varnish which you can get from a luthier very cheap (had ones for $30-40)

For those asking, the guitar is a Yamaha FG345, my father got it in his teens and he's in his sixties now. Honestly can't tell you guys what gauge the strings are, I haven't changed them in years (I love the sound of dead strings, and these ones in particular just feel right). The strings detune when I'm not using the guitar and only during the summer. I leave the guitar in a stand when not in use. Would it be better to leave it in my black soft case and leaning against the wall, in the coolest room I can find?

The strings are not detuning A LOT between every session, just on especially hot days it's noticable that the heat has taken it's toll on the strings.

Yeah, its normal for hot days to detune guitars. There isn't any substantial proof of this, but down tuning your guitar or tuning to an open tuning may allow you to maintain the tuning longer in heat. Just a theory I've had for awhile.

You should consider getting the strings changed. I would highly recommend high gauge strings. You are probably using 9s or 10s, and I would work my way up to 12s/13s for a deeper, brassier tone that can stay in tune over longer periods without retuning. Thats just my personal preference. Also, I'm concerned the rosewood on the fret board isn't being properly treated with oils. There are risks of cracking and decay when you don't maintain cleaning and taking care of an instrument over extremely long periods of time.

Also, depending on how often you and your father have played it, it could be time to change the frets. This is all hypothetical tho, because I haven't actually seen the guitar myself.

put your guitar in a case

the strings being detuned is, rather obviously, an indicator for the air having some potentially harmful effect on the guitar.

If you play guitar you would know that strings can get detuned even within an hour and sometimes even less. I've had strings get detuned as I'm playing a live. Not much, just around a semitone, but its still noticeable by ear.
Guitar strings get detuned constantly thats why most good guitarists will tune every time they grab their guitar.

I do know that, I was just pointing out what the strings being detuned "has to do" with damage.

i shouldve said this but the strings might need to replaced. Old strings have lots of detuning problems, and so do brand new strings. Need like 3-4 days with new ones to get them adjusted to the tension