Hello! The short answer is that public WiFi networks are just unsafe.
The chances are extremely small, and with the addition of https (or the green lock), the chances of hackers getting your information are even smaller. The hackers would have to be in close proximity to you and the network. They can’t be all over the world at every coffee shop. If your computer is infected with malware, you are already at risk, so being on a public WiFi network wouldn’t matter.
There are still a number of ways for hackers to get information from you on a public WiFi network. One way is called a “Man in the Middle” attack. Hackers set up a fake WiFi network that looks like an official hotspot or they gain access to a poorly protected network, then they sit the middle of you and the website you are attempting to access and they capture your information by routing you to a fake website where they get your login information before passing you to the real site.
The only way to truly stay secure on a public WiFi is to use a VPN (Virtual Private Network). They can be a little tricky to set up. The only two I am really familiar with are Private Internet Access and the Opera web browser which offers a free VPN built-in. Googling and reading reviews of various VPNs will lead you to more options. If you don’t have a VPN I would just make sure not to do any online banking or shopping while on a public network.
To make sure you are secure it’s also best to enable two-factor authentication on your most important online accounts. I have it turned on for my Gmail because all my other accounts are tied to that email address. Online bank accounts and other important sites are starting to enact their own security measures by asking you to verify your account when you are on a new network anyway. This also helps a lot.
I hope that helps answer your question,