lift the pots every day get used to the weights just after watering and when they feel light its a good method to tell when you need to water
That’s one way :-D
I also bought a sensor (analog), it has 2 pins on it and you simply poke it into the earth and it will show you dry humid or wet. It seems to work fine. Only concern I have is damaging the roots by poking it into the dirt too often. Now I try to measure as far as possible from the plant itself but it might not give you the best idea of the humidity close to the plant..
At least it’s better than nothing. I hope my plant won’t die on me with this hot wether and me not being at home to water them regularly :-/ well, starting from the end of the week, the temperatures will drop down to 15 degrees Celsius again (and not much sun :-( )