I’ve noticed a similar effect when it snows here in london. It’s unusual and it’s like a common adversary to everyone and everyone becomes more chatty on public transport
"Interestingly, while the data suggest that this perturbation may have a strong effect, a notable percentage of individuals were not consciously aware of the reason behind it. Given that attention is socially influenced (e.g., the phenomenon where people instinctively look toward the same point of interest as those around them), we can hypothesize that the pattern of awareness triggered by a disruption in routine may be socially transmitted, extending beyond its original cause. This may also help account for the subset of participants who reported not noticing Batman but nevertheless offered their seat. A speculative interpretation is that the disruptive effect can operate at an interpersonal level: shifts in attention or prosocial cues triggered in some individuals may spread socially within the group, influencing behavior even among those not directly aware of the initial disruption, consistently with research on the social contagion and interpersonal synchrony of prosocial and emotional behaviors."