Year Jan. Feb. Mar. Apr. May. Jun. Jul. Aug. Sep. Oct. Nov. Dec. 24-Hour Annual Avg. 2016 18796 18597 18408 17565 15086 2017 14243 16817 17847 18847 19212 19203 18117 18344 18027 18394 17584 15370 17667 2018 16473 17051 17530 18969 19083 19541 19268 20299 19780 19708 18126 16560 18532 2019 16704 16902 18433 19856 19386 20113 18964 20070 19865 19167 18312 15978 18646 2020 15252 16091 14107 11370 14357 15888 16289 16914 16751 16216 15431 15333 2021 14525 14704 16537 17350 17400 17956 17672 17700 17610 17474 16526 16357 16818 2022 14383 15713 16732 17170 17627 18142 17500 17452 16840 2023 2024