If you planning to travel to Big Arm State Park, Big Arm, Montana, 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 12:30 PM. The temperature feels like 49.45 with a humidity level of 43 so dress accordingly. Cloud coverage is 7 percent with visibility at 14.9 percent. Today’s UV index is 8, don’t forget the sunscreen if you need it! Today’s winds are traveling south at a speed of 5 MPH. At the end of the day don’t miss the sunset at 2:42 AM.