Swollen hands….due to increased exercise????

You can drink too much water and drown yourself, no joke. Doctors recommended amount is 2.5lt min - 4 max

There are about 101 different reasons your body can decide to retain water... most are temporary and harmless. If you ate more carbs than usual, being too hot, etc. can all affect it.

I see my doctor for any edema (swelling)

If your arms are a problem specifically, it may help a little if you hold your arm above your head, then gentle-stroke massage your upper arm toward your shoulder for maybe 30 seconds to a minute, then lower arm toward upper arm, hand toward lower arm, and repeat a couple of times.

ETA: I was taught that massage technique by a physical therapist who specializes in lymphedema treatment/avoidance for breast cancer survivors with certain surgical histories (which I am). OP, I'm not saying you're risking lymphedema - no reason to believe that - just explaining where I learned about that so it doesn't seem like I'm making it up. 🙂

I've noticed that - despite being an active person long term, good CV fitness, and not now overweight - that I'll sometimes get a bit of hand swelling on walks during hot weather (presumably because my hands are below my heart, and not much active while walking). For me, even though it makes me look like a weird freakin' idiot, it can help to hold one or both arms over my head for a minute or two a few times during the walk. It's not a radical difference, but a little help. YMMV.

While it's true that you can drink water to the point of literal death, it takes quite a lot, all at one time or close. It truly is important to get enough, especially in hot weather, especially during exercise.

Counting what you drink is possibly a good idea, but a better indicator would be looking at your urine. If it's a dark color, like dark mustard to brown, that's a bad sign, and you need more intake. If it's pale yellow, kind of straw colored, probably in a good range of fluid intake. (It can be kind of fluorescent-bright light yellow if you're getting more than you need of certain water-soluble vitamins, but that's generally not dangerous.) If it's very clear, you're probably getting more than ideal fluid intake.

How much you need can be quite individual. As a person who sweats lots, even when only at moderate exercise intensity and moderate temps, I need more than someone who sweats less, and need really lots if I do intense exercise outdoors in the heat. If the scale fluctuations don't freak you out, you can weigh yourself before and after an exercise session to get a rough estimate of whether you've lost a lot of water through sweat/respiration during the session - whether the water you drink during the exercise is leveling things out more or less. (You don't need to get it to completely neutral water gain or loss during exercise, but a big drop would suggest you might beneficially drink more, and consider electrolytes in the drink . . . though electrolytes aren't typically essential in mild exercise, or sessions less than a hour.)

Keep in mind that pretty much all fluids count, not just water, but other beverages (including tea and coffee, according to the most recent research), plus fluid in fruits, veggies, soups, etc.