Aside rare acid rare and a slight impact on solar generation, weather and the elements still don’t feel all that impactful. I think a nice addition to the game would be some weather that would actually push players to be prepared to adapt and fear the weather as not just a nuisance (like rain) but another separate entity to take account for.
Weather effects like fog and fallout would make travel more hazardous and nudge players towards sometimes saving projects for “rainy days” when travelling outside would be too hazardous.
Fallout would deal gradual radiation damage to players not fully covered and would urge players more to consider taping their windows shut, since toxic gas or smell is more of a passing nuisance than deadly.
Fog on other hand would act like nighttime in that it would block sight and would discourage vechile travel, but would be possibly advantageous to use to go on scavenging runs while the monsters senses are dulled.
Something along the lines of Stephen King’s The Mist might be fun, but that would probably require better region handling, so it could show up in certain parts of the overmap, pouring out of a local portal.
Bio, I have a challenge for you. Pick ‘Evacuee’ scenario, pick a world without cities, 1.0 items spawn. Then burn your evac shelter to the ground. You may have problems with boiling water during rainy days. It may rain for a LONG time. Sometimes you do not need fog, toxic fallout and other weather effects to fight for survival. But I like your idea. I wish that someday Cataclysm would be more dangerous in terms of environment
Permafrost could be a devastating one. Fall/winter the ground becomes sturdy and frozen, then when summer comes by, whatever structure is built on top of it collapses/sinks in. It begs the question why you’d build anything on top of it, though. Maybe it’d made for a good seasonal stakeout. xD
I don’t see boiling water as an issue, since food poisoning to me has always counted as more of a nuisance than a threat.
Great minds think alike 
I’m still grumpy about the 90-day months, but meh, there’s an option for changing that on the world creation screen, so whatever. 
One mod I’d definitely like to see would be one that:
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introduces more special types of weather that affect strategic or tactical situations, such as fog, acid rain, fallout, downpours, cold snaps, heat waves, and so on.
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Gradually causes the seasons and frequency of serious weather events to become more severe, such that the max/min temperatures gradually become harsher due to changes in the weather wrought by damage to the planet’s environment and such.
Basically right now Cataclysm has a lot of modelling and gear for dealing with all of these sorts of conditions - but frankly most characters now live in the nearly eternal gentle conditions of the first 180 days of spring/summer where you really don’t NEED any of that gear, and by the time winter does roll around, it’s just a blessed excuse to put on your really heavy armor gear for the extra warmth & protection - not an existential hazard of any sort.
Towns/cities have roaming zombie hordes.
The wilderness should have giant insects, Triffids, fungus, mi-go, unearthed horrors, and nether creatures.
Zombies have evolution, the rest need terraforming including impacting the local weather. Fungal towers will spawn more towers over time and the change the weather in a radius around it. Mines keeps leaking more and more fog that allow unearthed horrors to roam further and further on the surface.
Surviving in your cabin and never leaving would become harder as the year goes by and the Earth keeps changing without your proactive work.
still by the time you reach the point where evolution is noticeable those threats are insignificant cause you’ll already have installed enough bionics to kill an entire hospital pop without a scratch