The effects of temperature on reported cases of a number of foodborne illnesses in England and Wales were investigated. We also explored whether the impact of temperature had changed over time. Food poisoning, campylobacteriosis, salmonellosis, Salmonella Typhimurium infections and Salmonella Enteritidis infections were positively associated (P<0.01) with temperature in the current and previous week. Only food poisoning, salmonellosis and S. Typhimurium infections were associated with temperature 2-5 weeks previously (P<0.01). There were significant reductions also in the impact of temperature on foodborne illnesses over time. This applies to temperature in the current and previous week for all illness types (P<0.01) except S. Enteritidis infection (P=0.079). Temperature 2-5 weeks previously diminished in importance for food poisoning and S. Typhimurium infection (P<0.001). The results are consistent with reduced pathogen concentrations in food and improved food hygiene over time. These adaptations to temperature imply that current estimates of how climate change may alter foodborne illness burden are overly pessimistic.