Firstly, I've been thinking on this for a while.
While I haven't watched the show that inspired this biome, I absolutely love the aesthetic of this biome. The care and attention to detail that's gone into this mod really shows

Having said that however, the burning rain itself may need some further attention.

Because I've seen other users report similar issues, I felt it worth while to bring attention to how boiling weather functions and the issues it causes.

Based on how the rain is described, (to me atleast) it sounds like boiling weather should just be really hot water falling from the sky.

The Problem:
It functions like magic water bullet weather that can reliably inflict permanent organ damage to your pawn wearing full marine armor, simply because they didn't stand under a roof.

• Boiling weather (drizzles, rains, etc) cause burns to anything that is in the rain. This itself isn't a huge issue.
  
• Injuries seem to ignore the logical order of protection and body parts (i.e. apparel > skin > internal organs). The first burn a pawn receives can easily be their brain, or liver
  
• These wounds seem to scar fairly often; and some organs always scar from any damage.
  
• Leaving aside other mods (which a user might not have) in vanilla - scars are incredibly difficult to cure short of exotic items, luciferum, or certain archotec genes like scarless.
  
• The frequency of rain in the biome, and the frequency that these injuries can occur, makes boiling weather exceptionally punishing.

Now having listed these issues off; I do want to say I don't feel there's anything wrong conceptually with boiling weather. It feels at home in a wet, verdant forest biome that's the result of some glitterworld corpo trying and failing to make a theme park.

To me, the issue is entirely with how it randomly inflicts injuries, and the permanent debilitating scars it inflicts add up over the life of a colony. If there was a way to protect against it, or even if it simply couldn't damage anything beyond skin.... I might leave the damage enabled for the challenge of it. As of now, the only option I seem to have is to roof everything and treat the rain like super toxic fallout.

Toxic weather atleast gives the player time to use their pawns outside, racing against time (the toxic ailment) plus various options to extend that timer or completely protect from the weather's effects (such as protective apparel and genes)

I might suggest the weather be changed to something similar to a toxic weather, but less severe; and I say this because the boiling forest is meant to be a thriving, verdant biome with a lot of vanilla animals happily living there. The weather can't be as fatal or severe to the animals like toxic weather is - but not as permanently impactful to player pawns as it is currently with the random scarring it does.

So as an alternative, perhaps the weather could inflict it's own 'boiling' ailment; something that is unpleasant and painful with enough exposure. Animals won't mind it so mush, but it would be impactful to players; while still giving a 'timer' (like the toxic exposure ailment gives) to race against to do outdoorsy chores.

The nature of the ailment could simply be a simulation of standing out in scalding hot rain - incredibly painful, and with enough exposure, causing scalding wounds.
Initial exposure could simply be pain; with later levels of exposure causing worse pain and inflicting a 'blisters' condition on the 'body' part.

This would be in keeping to how the rain tries to work now; but treating this more like what it is: 'the pawn was scalded badly by rain'
And less like 'the pawns stood in the rain and now has severe permanent brain damage'.

Alternatively, the rain could inflict a more exotic ailment, maybe it's hot yes - but as a side effect of what this mysterious corporation did, there's mechanites in the water that do strange things. Things that make it feel like your skin is boiling - and I dunno, maybe a mix of positive and negative effects a la 'sensory mechanites' so a player has some reason to not go 'Dirtmole mode' on a forest biome?
Could be fairly potent given how often it rains, but perhaps balanced by the fact that any animals and raiders would also get rained on too...