Figure 2 : Temporal variations in frost timing.

From: Observed variations in U.S. frost timing linked to atmospheric circulation patterns

Figure 2

(ad) Day of year with last spring frost in the North region (SN), the Central region (SC), the South region (SS) and the West region (SW), shown with hemispheric annual mean near-surface air temperature (TH). Note that the ordinate is reversed for TH to facilitate comparison to the S indices. (eh) Day of year with first fall frost in the North region (FN), the Central region (FC), the South region (FS) and the West region (FW), each shown with TH. Trend lines are shown in each panel indicating presence (solid) or lack (dashed) of statistical significance at the 95% confidence level.