Past meteorological records are important for improving our understanding of past, present, and future climates. Imaging and digitization of historical paper-based instrumental meteorological records must be carried out before these records are lost to decay. This kind of activity called “data rescue” is now taking place at many institutions around the world. A data rescue project is underway to preserve Japanese instrumental meteorological records from the 19th century. These data were collected by foreign residents and visitors, Japanese scientists influenced by Dutch science, and by Japanese merchants. Recently, meteorological measurements taken at Mito from 1852 to 1868, and at Yokohama in 1872 and 1873 have been found. Based on instrumental records collected through this data rescue project, a warmer climate in the 1840s and 1850s around the South-eastern Kanto Region has been identified. Large year-to-year variations of winter temperatures have also been detected.