In the face of the current focus on climate change, the question whether climate variations have effects on ethnic violence is addressed. This article shows the results of an empirical study on the relationship between violent livestock raiding and climatic conditions. The practice of livestock raiding causes large numbers of casualties in northern Kenya. While conflicts over scarce resources may be largely explained by drought conditions, population pressure, and access problems, livestock raiding is more violent during wet seasons, when pasture and water are abundant and when the livestock is in good health. The higher incidence of violent deaths during wet times hints at opportunistic behaviour of raiders.