it could be cold? but why does that matter? single resists are for crazy optimization, just stack some all resist and you will not die that much by them. and what level are you playing and having trouble with them? you could use some toughness boost if they boast a challenge.
ok this does change some facts. i thought you might be just leveling to 70 in a difficulty higher than you should, or running rifts without bis gear. well trust me, in a GR100 you just dont play a rift with ghosts, whatever you do they are going to destroy you anyway. its nothing on your end, and there is nothing you can do about it, just reset rift. i sometimes die on them on 80s speeds, those and goat men can fuck my wizard even in lower rifts.
Assuming you use the standard build with Teleport - Calamity and Aetherwalker, then either stun them by teleporting straight on them or teleport a few screens away. In those high GRs its also key to maximize the effect of Calamity together with your Ancient Parthan Defenders (APD). Big density is not only needed for progress in the rift, but also for getting the required toughness boost. When the density is high enough you might even be able to survive a few ghosts.