How to get a specific index of a string?

Im currently working on something in JAVA, and i was wondering what is the best way to get a specific index of characters within a string..

Lets say I want to check something like that :

<title>Saturday - 14:00 GMT: Light Cloud, 3°C (37°F)</title>

How can I check the specific index of the String (GMT) to pass it to a switch statement and display the appropriate picture -> in that case "Light Cloud"?? Note that the day might change (bigger or smaller index will give different value so it shouldn't have a specific startPoint)