I find if my hair is wet, I instantly feel lots cooler. Maybe try frequent showers or wetting your head. This is particularly useful just before bed, as it cools you down enough to sleep.
Working in the library is an excellent idea. I always got a lot more work done in grad school when I wasn’t at home.
Have you heard of chemical dehumifiers?
Chemical adsorbent dehumidifiers absorb moisture from the air with a “desiccant” - a drying agent such as silica gel or plain road de-icing salt.
The wet salt solution drips into a pan or floor drain, drying the air. Because the salt runs off with the water removed from the air, it must be replaced after two-three months. The system has no moving parts and isn’t electrical. It’s really just a plastic basket of salt with a container beneath it in which the water drips that you empty every week or so. They’re quite cheap. You can buy them, in the Netherlands anyway, in DIY stores. People use them to keep un-used caravans or basements/garage’s dry.
Something else: do you dry your laundry on a clothesline, outside, or do you have a dryer in your home? A dryer in your home could add to the humidity.
Cheaper than blackout shades, more efficient than aluminum foil, readily accessible to the less-than-handy: styrofoam insulation panels! I bought thin sheets of styro from Home Despot or such, cut it to the proper size (use a serrated knife,) and popped it into the windows to cut down on heat a couple of summers ago. It worked well enough that I bought a couple of rolls of neutral wallpaper and glued it to the styrofoam, making them a permanent part of the “decor.” In my case, I’m trying to cut my a/c bills, but it would also help keep your apartment cool, pasunejen. Just cover your sun-facing windows, and uncover the ones you want open for circulation purposes.
(I don’t recall the exact product name, but it seems like the styro I bought is actually sold as insulation to go behind vinyl siding – backer boards, maybe? IIRC, a sheet of the foam is about 4x8 feet, and not very expensive at all. I think I bought three sheets for ~ $25, to cover a dozen windows of varying sizes. If that’s too much, furniture stores probably throw out a lot of large styro sheets from packing crates.)
This won’t cool your apartment but it will cool you and that would help, yes?
I went to the store and bought (for numerous other purposes, it’s usefullness cannot be overstated), an oversize aluminum tub. I got mine at a farm store but you could as easily use a tub for cooling beer, made of plastic. The main thing is it should be deeper than a bucket and flatish on the bottom. Ideally you want the water to reach almost to your knee.
The suggestion that bathing your feet will cool you down is a good one, but ankle depth is hardly worth the effort in my experience. Deeper bucket/tub, however = markedly better results.
Spread a thick towel in the bathroom, put the tub on one end and fill with cold water. Whenever you’re feeling hot, step into your bucket, it will work in just a few seconds, you will feel soo much better, and you’ll be in the bathroom where it’s very handy to dry off your tooties and continue along your merry way.
This really does work and it got me through a very, very hot and sticky summer spent in sweltering student digs.
Or, if you have a laptop, pay a visit to the local coffee shop and do your work there when it gets too hot to stay in your apartment. When J.K. Rowling was broke and working on her first Harry Potter book, she went to a coffee shop and worked there to keep warm in the winter.