If you planning to travel to Big Thunder Gold Mine, Keystone, South Dakota, here is your 6-day travel weather forecast to make sure you have all the essentials needed during your stay. Start your day when the sunrises at 2:25 PM. The temperature feels like 40.900000000000006 with a humidity level of 40 so dress accordingly. Cloud coverage is 58 percent with visibility at 14.9 percent. Today’s UV index is 2, don’t forget the sunscreen if you need it! Today’s winds are traveling west-northwest at a speed of 7 MPH. At the end of the day don’t miss the sunset at 11:20 PM.