Access to West Thumb Geyser Basin Access to Visitor Information Center. West Thumb Geyser Basin features dump an average of 3,100 (11,733 liters) of geothermally heated water into Yellowstone Lake every day. Despite this volume the lake is only slightly affected very near the shoreline. The average summer temperature of Yellowstone Lake is only 45 degrees F (7 degrees C). With half of the earth’s geothermal features, Yellowstone holds the planet’s most diverse and intact collection of geysers, hot springs, mudpots, and fumaroles. Its more than 300 geysers make up two thirds of all those found on earth.