The natural world is a complex and fascinating study subject. Now add primal spirits, gods and magic into the mix and it becomes significantly more complicated, and interesting.
WIP
Many climatologists prefer to avoid interference with nature if possible, allowing the natural processes to occur unimpeded is the best way to study them. However, when needs must, the forces of nature can be weaponized to a variety of ends from conservation to destruction.
WIP
Some kind of primal sense?
ranger-like bonuses against natural difficult terrain and natural hazards (7th?)
Determine source of weather/climate effects (e.g. you can tell when a mist is natural or magic)
Advantage against regional effects of creatures
Control Weather?
Maybe choose a specialist terrain like land duid or ranager
Starting at 3rd level, you always have certain spells prepared after you reach particular levels in this class, as shown in the Climatologist Spells table. These spells count as lorehunter spells for you, but they don't count against the number of lorehunter spells you prepare.
Climatologist Spells
Lorehunter Level.3rd | Create or Destroy Water, Ensnaring Strike5th | Gust of Wind, Warding Wind9th | Call Lightning, Sleet Storm, Wind Wall13th | Blight, Freedom of Movement, Ice Storm17th | Control Winds, Commune with Nature, Insect Plague, Maelstrom, Wrath of NatureAt 3rd level, you gain proficiency in the nature and survival skills if you don't already have them.
In addition, you have advantage on ability checks you make to determine the source of weather and climate effects. For example, you may be able to determine if a fog is naturally occurring, the result of a magical effect, the result of neaby industry or even a nearby creature's lair.
A little vague and situational
Starting at 3rd level, you can use a bonus action to subtly alter the environment in a 15-foot-radius sphere, centered on a point you can see within 60 feet. Choose one of the effects listed below, the area is filled with the chosen effect for 1 minute, or until you are incapacitated. As a bonus action on subsequent turns for the duration, you can move the area up to 30 feet or change the effect but not both. If the effect allows a creature to make a saving throw, the saving throw uses your lorehunter spell save DC.
You can use this feature a number of times equal to your proficiency bonus, regaining all expended uses on a short or long rest. If you have no uses remaining, you can expend a spell slot of 1st-level or higher to use this feature again.
Could make it an emenation?
Acidic Precipitation. When a creature enters the area for the first time on a turn, or starts its turn there, it must make a Constitution saving throw or take 1d6 acid damage. A creature take half as much on a successful save.
Arid Air. Creatures that start their turn in the area are hampered and distracted until the start of their next turn as their throats and skin become uncomfortably dry. Creatures submerged underwater are unaffected.
Boiling Heat. When a creature in the area takes fire damage, it takes an additional 1d6 fire damage. When a creature in the area takes cold damage, the cold damage is reduced by 1d6 (to a minimum of 0).
Damp Air. Creatures in the area have disadvantage on Constitution saving throws against cold damage, poison damage, the poisoned condition or disease.
Freezing Cold. When a creature in the area takes cold damage, it takes an additional 1d6 cold damage. When a creature in the area takes fire damage, the fire damage is reduced by 1d6 (to a minimum of 0).
Obscuring Mist. The area is lightly obscured by a natural looking mist. A creature can make an Intelligence (Investigation) or Wisdom (Nature) check agaisnt your lorehunter spell save DC to determine that the mist is unnatural.
At 3rd level, you know the elementalism cantrip. It counts as a lorehunter spell for you, and Intelligence is your spellcasting ability for it.
In addition, when a creature you can see within 15 feet of you makes a Strength or Dexterity saving throw, you can cast the spell as a reaction to impose a 1d4 penalty on the roll as you manipulate the environment to distract or destabilise them. You can use this reaction a number of times equal to your proficiency bonus, regaining all expended uses when you finish a long rest.
Starting at 7th level, when you hit a creature inside the area of your Microclimate with a weapon attack, you can push them up to 10 feet in a direction of your choice.
Starting at 7th level, moving through difficult terrain costs you no extra movement. In addition, being lightly obscured by weather, such as rain or fog, does not impose disadvantage on your Wisdom (Perception) checks. Finally you take half damage from falling as you cushion yourself with wind, snow or mud.
Starting at 11th level, you can choose to target a either a 15-foot-radius sphere or a 20-foot radius sphere with your Microclimate feature.
Additionally, you can use a bonus action to force all creatures inside your Microclimate area other than you to make a Constitution saving throw against your lorehunter spell save DC. A creature takes 2d6 acid, cold, fire or lightning damage (your choice) on a failed save or half as much on a successful one.
a bit meh
Starting at 15th level, as a bonus action, you can ride the winds themselves and gain a flying speed equal to your walking speed for up to 10 minutes. If you are in an area of high wind, such as a storm, your flying speed increases by 10 feet for this duration. If you fall while under these effects, you take half as much damage from falling.
Once you use this feature, you cannot do so again until you finsh a long rest, unless you expend a spell slot of 3rd-level or higher.
Maybe this should be 11th level instead (given fly is a 3rd level spell).
Could make it a big jump instead
At 3rd level, you know the elementalism cantrip. It counts as a lorehunter spell for you, and Intelligence is your spellcasting ability for it.
In addition, when a creature you can see within 15 feet of you makes an ability check or saving throw to avoid being grappled, knocked prone or moved against their will, you can cast the spell as a reaction to hinder them using the environment around them. You might push them using wind water, trip them with soft mud, distract them with embers or any other suitable effect you choose. You impose a 1d4 penalty on the target's roll. You can use this reaction a number of times equal to your proficiency bonus, regaining all expended uses when you finish a long rest.
At 3rd level, you know the druidcraft cantrip. It counts as a lorehunter spell for you, and Intelligence is your spellcasting ability for it.
In addition, when a creature you can see within 15 feet of you makes an ability check or saving throw to avoid being grappled, knocked prone or moved against their will, you can cast the spell as a reaction to hinder them using the environment around them. You might push them using wind or water, trip them with soft mud or vegetation or you might distract them with dust or spores. You impose a 1d4 penalty on the target's roll. You can use this reaction a number of times equal to your proficiency bonus, regaining all expended uses when you finish a long rest.
Some bonus, ideally one that is not covered by evolving cantrips
Track pollution/disease source.
replicate a smell, and/or determine source (i.e. creature that made it)
Could swap this for gust
Additionally, you have advantage on saving throws against natural hazards and weather effects such as blizzards, extreme heat or frigid water. Such hazards and weather effects do not impose disadvantage on your Wisdom (Perception) checks and you have resistance to damage caused by them.
The second part is maybe a little vague, also slightly clashes with Careful Stride
Dispersing Breeze. Wind in the area blows rapidly, dispersing smoke and fog, including from the fog cloud spell, and extinquishing nonmagical fires.