You can start using this now here : https://salford.idm.oclc.org/login?url=http://jcr.incites.thomsonreuters.com/
The old platform will be retired at the end of December.
What is Journal Citation Reports? Thomson Reuters say :
Journal Citation Reports® offers a systematic, objective means to critically evaluate the world's leading journals, with quantifiable, statistical information based on citation data. By compiling articles' cited references, JCR helps to measure research influence and impact at the journal and category levels, and shows the relationship between citing and cited journals.
Now offered on the InCites platform, access and explore the underlying data that informs JCR metrics from citation networks to self-citations. This expanded capability lets you conduct analysis and comparisons of citation relationships across journals and categories over time. You can even localize your analysis to understand publishing practices within your organization.