Since most trails here have very little shade, be prepared for a dose of sun and heat if you hike in mid-day. On the other hand, when the marine layer is strong, it can be quite cool on any trail, but especially the Vernal Pool Trail, with temperatures in the 50s, and the cold wet wind stealing all one's heat away. Ticks and adult rattlesnakes are present. Staying on the main trails will drastically reduce your chances of seeing either varmint. So far, they are bad only sometimes in shaded wind-sheltered areas.
Mosquitoes are troublesome around the tenajas.
Overall, bugs here are far less of a problem than they are in most natural places in California at this time of year. For more information about all of the above, see Detailed observations .