I think this has been mentioned but just in case putting this in spoiler brackets. Reason guy was bemoaning about "that thing is coming" is because he and Rosa are mages and "that thing" is a type of magical storm. It might overload the environment with too much magical energy or something but what happens is nobody can use magic at all, and magic users will experience headaches while feeling enervated (little if any energy) and crappy. While some buildings have special measures to prevent the physical symptoms from bothering people they still can't use any magic. What this means is that as soon as the storm hits both he and Rosa won't be able to cast magic which seems to be their only means of offence and defense. Furthermore, any rescue party will have to be comprised of people who can go that far in Silicon without having a healer or mage. Also, even if do rescue her and bring her and any injured to the hospital the healers can't use any healing magic during the storm and doesn't seem like they have healing potions so even treatable injuries could turn fatal if the storm lasts long enough. Especially if doctors focused more on healing magic as a quick fix and not enough on stabilizing or treating patients without magic like during a storm.