I suggest more types of rain. At the moment we only have Normal (stable at about 3.8-4.1mm) and Heavy (stable at 5mm but rare)
I suggest to add a light rain (stable at somewhere around 1.5-2.5mm) -if possible with darkskys limitations- and maybe reduce normal rain to just over 3mm, so that not all rain races are 4mm snorefests. Who knows, maybe even have it so it can be stable at just under 1mm to really spice things up, without having to add RNG.