Earliest day in the year at PL 4: June 10, 2002.
Latest day in the year at PL 4: October 13, 2020.
Longest duration at PL 4: 41 days from September 1, 2005 to October 11, 2005.
Years level never moved above PL 4: 1992, 1998, 1999, 2005, 2011, 2012, 2014, 2016, 2022, 2023.
5-year average number of days per year at PL 4: 18.
10-year average number of days per year at PL 4: 19.
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