Records are provided for five southwestern North American (including Mexico) species of Ephemeroptera by way of initial reports of Camelobaetidius similis from California and the USA, Cloeodes peninsulus from Arizona and the USA, C. excogitatus from Oregon, Homoeonueria alleni from Montana, and Lachlania saskatchewanensis from Nebraska. All records represent notable northern range extensions, except for the record of L. saskatchewanensis, which is an eastern range extension within the USA. Short discussions regarding the significance of these distributional data are also provided.