A couple of weeks ago I've posted here regarding humidity in our house as I noticed it went up to ~75% indoors. I've bought a dehumidifier, but noticed that the humidity went up again after dehumidifying a room to eg 60%. Then, I installed a temp/humidity sensor outdoor and also calculated the absolute humidity to be able to compare easily. And... then I noticed when it's moist, like now, the outdoor humidity would be close to 100%. Thus, it would almost be impossible to get it <60% indoors, unless you would heat it to 25c +

Right now, it's 99% humidity @ 11c outside, which comes to 9.9g / m3 absolute humidity:

In the bedrooms it's 16.4 @ 65% which is as expected. In the living room it's 21c @ 55% which is almost the same absolute humidity as outside:

Still, it's important to heat your rooms to ensure RH doesn't reach 100% as that may cause dampness/mould. I've installed temp sensors & panel heaters in all rooms and set the min temp to 16c.