Climate change is predicted to increase the transmission of many vector-borne pathogens, representing an increasing threat to a safe blood supply. In early 2011, Australia experienced catastrophic rainfall and flooding, coupled with increased arbovirus transmission. We used Ross River (RRV) and Barmah Forest (BFV) viruses as test cases to investigate the potential risk posed to Australia’s blood supply after this period of increased rainfall . We estimated the risk of collecting an infected donation as one in 2,500–58,000 for RRV and one in 2,000–28,000 for BFV. Climate change may incrementally increase the arbovirus threat to blood safety.