Figure 10: Spatio-temporal distribution of SPEI-3 drought conditions in Iowa.
Figure 11 presents the Palmer Drought Severity Index (PDSI), which reflects the cumulative effects of temperature and precipitation on soil moisture over extended periods. The PDSI confirms the prolonged nature of the 2012 drought, particularly in southern Iowa, while also identifying significant moisture surpluses in 2008 and 2010. These findings validate insights from SPI-3 and SPEI-3 while emphasizing PDSI’s utility in understanding sustained drought and wetness impacts. Mild droughts in 2006 and 2015 and moisture surpluses in 2014 and 2016 further highlight localized variability, suggesting the influence of regional climate anomalies.