Zhiheng Wang and Doantam Phan, posting on Google’s Webmaster Central Blog:
The “Speed Update,” as we’re calling it, will only affect pages that deliver the slowest experience to users and will only affect a small percentage of queries. It applies the same standard to all pages, regardless of the technology used to build the page. The intent of the search query is still a very strong signal, so a slow page may still rank highly if it has great, relevant content.
You can check here whether your website is mobile-friendly. It’s time to start shedding that extra weight.