Deadly Weather

My take on this set: These three cards all try to do something similar, but with varying success. They come down on your location and stay there until the end of the round. While there, players are encouraged to leave the location either through penalties while there, by punishing them if they end their turn there … or both.
This set is used for the first half of the campaign and unless you take a detour through the Fatal Mirage or skip some of Ice and Death, chances are that you have to deal with these cards for your first four scenarios back to back to back to back.
They gain some additional context from cards in those scenarios. Ice and Death has Zero Visibility in it, a card that makes moving in and out of locations with attachments cost and additional actions. Deadly Weather is not the only encounter set that plays into that card, but it’s the most important one.
Forbidden Peaks makes these cards more impactful on their own, as movement option in that scenario are very limited. Unless you manage to clear the location from clues, the only way to dodge these is moving backwards which has a host of other issues coming with it.
As a result, this ends up as a set that can have a noticeable impact in spite of the cards in it not being that threatening by themselves.
Something else of note: With Protective Gear, there’s a player card in Edge of the Earth that is tailored almost specifically to countering this set. And the campaign itself offers Roald Ellsworth as another way to neutralize these.

What it does: Antarctic Wind attaches to the nearest location that doesn’t have a copy of it attached, so usually to the location of whoever drew the card. It stays there until the end of the round when it gets automatically discarded. While in play, investigators at its location are unable to play or draw cards.

My take: A rather mild treachery in most cases. Comparable to Dissonant Voices from the Core Set, but affects everyone at the location. On the other hand, it can be sidestepped by simply leaving the location. This gives a good amount of counter play and makes the situations where you are directly impacted by this quite rare.
It is a more impactful card for investigators that are event based, like Diana (who will be left without the ability to throw cancels at any further encounter cards drawn that turn) or Nathaniel (who’s suddenly unable to properly fight anything at that location).
It sticks around until the end of the round which means it will prevent you from drawing a card in your upkeep if you end your turn on its location.

Threat level: Low. Contextually relevant for some investigators, but often nothing to worry about too much. Can go up to Medium if you are dependent on events to discover clues and/or if you are playing Forbidden Peaks.

Dealing with it: If it’s really a bother, move to the next location. You might want to in order to be able to draw in your upkeep anyways. Unless you are currently stuck with a Zero Visibility in your threat area, this will just cost a single action which is rather fair for a treachery.

What it does: Polar Vortex attaches to the location of the investigator who drew the card. It is automatically discarded at the end of the round. Anyone ending their turn at Polar Vortex’ location is dealt a direct damage to each of their cards with health. This includes the investigator card and story allies.

My take: Like Antarctic Wind, this card wants to force you into leaving its location. And it does a very good job at that, the damage really adds up if you have some allies or assets in play. Since it does count the partner allies, it will usually deal at least 2 damage.
If your partner is William Dyer, this one damage can even just outright kill him. But even if it’s not Dyer, the damage on those partners does persist through scenarios so avoiding any unnecessary tokens should be a priority.
I’ll pretty much always want to not end my turn on this location, even if it means taking an attack of opportunity from an engaged enemy.
This card is a lot more dangerous in Forbidden Peaks where it can force you to decide between taking the damage or going down a depth level.

Threat level: Mid. Ignoring this card is rarely possible. Mid to High in Forbidden Peaks.

Dealing with it: The actual thing to worry about from this card is not the damage, that part is easy enough to avoid. But it does more or less force you to move, which can be an issue if you are engaged, if you have Zero Visibility or when the only way to move is backwards.

What it does: Like Polar Vortex, Whiteout attaches to the player’s location and discards itself at the end of the round. Anyone at Whiteout’s locations suffers -1 to each of their four skills.

My take: Another mild one. Getting whipoorwilled (yes, that’s a word) for a turn isn’t too bad and usually not worth specifically leaving the location for. Of course the effect is not nothing and it might lead to failing a test, but it will be rare that this card costs the group more than the equivalent of an action or two.

Threat level: Low. Tests become harder for a turn, but it doesn’t have any lasting effects or more restrictive ones for that turn.

Dealing with it: It’s the weakest of the three attachments from this set. It’s worst case would be popping up on a location where you are currently fighting something, but in most cases this will just impact some investigation tests. There’s the possibility of having both of them stack on top of each other, but unlike with the Whippoorwills from Dunwich this is unlikely even in four player groups.