I recently did a hike at Pinnacles National Monument in Monterey County one very hot day. The park is about an hour from Monterey but feels like it is days away. The climate is completely different as the park is never impacted by the marine layer. The day we went was around 40C in the shade and likely well above that in the sun. Here is part one of the event starting with the camp site:
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The main highlight from the park are the caves you get to crawl through that house bats. In the heart of the cave, it was nearly pitch black while water could be heard running nearby. Not only was it a great break from the heat, it was very peaceful.