The Ontario in-filled climate data collection includes information from 339 monitoring stations maintained by the Meteorological Service of Canada. Historical climate data commonly has missing hourly and daily records due to equipment malfunctions, temporary site maintenance or other reasons. “In-filling” is a technical process that draws on data from nearby stations to fill in these missing records. This collection contains fully in-filled precipitation and temperature records for Ontario from 1950 to 2005. It is organized into eight separate databases in Microsoft Access format. One of the databases contains daily in-filled climate records. The remaining seven databases contain hourly in-filled climate records divided into regions for manageability.