The JCR which is part of the WoS gives the IF of last year, usually not the most recent IF. Therefore, you could enter the WoS (Clarivate Analytics), enter the of the journal (in the "publication name " field). The result of this search will give you all papers of that journal indexed in this database. Then go to the citation report (upper right side). This report gives you the total number of citations of each year, and it is updated. Then divide the citations of 2018 by the number of publications of 2016 and 2017, and you will get the most recent journal's IF.