In the Webmasters blog, Google announced that the effects of the mobile-friendly algorithm, which was launched on April 21, 2015, will be enhanced.
The update happened in mid-May and “increases the effect of the [mobile-friendly] ranking signal.” Google said that if your sites are already mobile-friendly, you don’t have to worry because “you won’t be affected by this update.”
When the update occurs, things will happen gradually, so as not to see a sudden collapse of non-mobile-friendly sites. The mobile-friendly algorithm is a page-by-page alert, so it may take time for Google to evaluate each page, and perhaps that’s why the release will happen gradually. And depending on how fast Google crawls and indexes all the pages on your site, the impact may be slower.
It is believed that this release will have less impact than the original mobile-friendly update called “Mobilegeddon.” The original Mobilegeddon was supposed to have a significant impact on mobile results, but not everyone said it had a big impact.