All you need is an

Aqara Waterleak Sensor:
https://www.aliexpress.com/item/32988557016.html?spm=a2g0o.productlist.0.0.45c56f23iStZQJ&algo_pvid=bfa3abef-e440-4dd2-beeb-8300913bfedf&algo_expid=bfa3abef-e440-4dd2-beeb-8300913bfedf-1&btsid=d9f2c050-5192-414e-948c-9ec333385e42&ws_ab_test=searchweb0_0,searchweb201602_2,searchweb201603_52

and a Raindropdetector:
https://www.aliexpress.com/item/32711871234.html?spm=a2g0o.productlist.0.0.449e6577VOnUzr&algo_pvid=122083a5-0b4d-44e2-9477-c74b04a92acc&algo_expid=122083a5-0b4d-44e2-9477-c74b04a92acc-0&btsid=ccbad3c6-067f-44a5-9fc6-bf75f2c16853&ws_ab_test=searchweb0_0,searchweb201602_2,searchweb201603_52

You can just pin the cable in the screws on the back of the rain sensor.