This is year around park although summer is very hot and not the recommended time
to visit. Winter can be cold especially at early morning. From November through
end of May you must make a reservation in the website (link below).
note 1: Because it is located in Las Vegas this is very popular park for hikes, bike
rides (one-way road) and rock-climbing.
During weekend the parking lots at
different trailheads can be full and the trail themselves will be crowded with many people.
Therefore, at winter the entrance to this park is by reservation only (check park website).
note 2: Make sure to make a visit reservation and day pass (Nov. – end of May).
thoughts: I visited here only one time, I did not had the time to hike so I drove the main scenic one-way road and
stopped at viewpoints along the road.