There is no definitive answer to this question as it depends on the specific definition of “journal.” Generally, however, a blog is not considered a journal because it is not typically published in a formal format (i.e. it is not typically edited by a single editor).
Additionally, many blog posts are written in a more informal tone and are not typically peer-reviewed. Taken together, these factors make blogs less likely to be considered a journal than, for example, a magazine or journal article.
While the distinction between blog and journal is not always clear-cut, it is important to consider the context in which a particular piece of content is being published. In general, it would be more appropriate to call any content that is not typically published in a formal format a “blog post” rather than a “journal article.”.