Specimen Ridge Trail hike. Petrified forest remains on the top of a foothill.
It was overcast and raining in Yellowstone, but that only added to the experience. I have been there 3 times in the last 10 years, and each time Yellowstone is different. I would highly recommend summer months, as the wildlife is in good abundance. This trip was in October -- mornings were usually a little chilly but sunny with blue skies, afternoons of rain and even sleet/snow, but then the storm would suddenly be over, the dark clouds would depart quickly, and the sun would quickly appear. One dreadfully wet and windy hike to Imperial Geyser ended with sudden sunshine followed by a huge rainbow precisely at the moment we arrived back at the car. The previous night the sun appeared just prior to Old Faithful erupting, photos below are of Old Faithful erupting at that moment (taken with iPhone, I left my good camera in the car thinking, pffft, everyone takes photos of Old Faithful.):