High temperatures have been linked to aggression in humans and recent literature has established a connection between climate change and violent inter-group conflict. Previous studies have emphasized economic mechanisms in explaining the effect of climatic conditions on conflict. Using data from two large-scale field experiments, we show evidence of a direct causal effect of high temperatures on nonviolent inter-group conflict, proxied by discrimination in helping behavior toward an ethno-religious outgroup. In our experiments, as temperatures rise, individuals faced with a choice to provide help to strangers in every-day interactions disciminate more against ethno-religious minorities. In light of expected increases in the frequency of temperature shocks due to global warming, our findings suggest that inter-group conflict of all forms will become more prevalent in the future.