My most loyal hiking partner, Bob G, had never hiked the Vivian Creek trail to San G before.  Although my trip to Mt Ranier fell through, I was still planning to backpack to Cottonwood Lakes in the Sierras, climb the rest of way to Mt Langley, and then finish the trip by hiking Mt Whitney oi a day.  I like to test myself and others on San G, to see if we are ready.  We were doing fine until we near the top and I noticed storm clouds brewing to the north, I think over San Bernardino Peak.  I  then heard thunder and asked Bob if he knew what the sound was.  He guessed “a sonic boom”, which was disappointing to me.  I explained to him that was thunder, and we could see the clouds getting darker and the rain falling out of the clouds.  I told Bob we would need to hurry off the top as the wind was kicking up.  We did that, and we were able to stay a little ahead of the storm clouds on the way down.