Average number of days without killing frost [map] : based on records from about 4,000 stations, of which about 600 cover the full 20-year period 1895-1914 / United States Department of Agriculture, Weather Bureau
Relief shown by hachures. On verso: Average growing season in four-fifths of the years -- Number of times in the 20 years 1895-1914 the season without killing frost was 15 days or more shorter than the average. Includes first killing frost in fall 1914 (inset map), duration of season without killing frost (chart), and text.