1. Average dates of first killing frost in fall. : based on records from about 4,000 stations, of which about 700 cover the full 20-year period 1895-1914 Maps University Of Minnesota Public content 1916. United States. Weather Bureau. On verso: Dates on which of killing frost in spring falls to 10 per cent -- Dates of which the chance of killing frost in fall rises to 10 per cent... The Department (Washington?).