Originally from Oz here.. but now living in WA.. have been for 12 yrs... and Im always cold..!! people laugh at me,,but damn Its cold.!!! lol
anyway. we have been in April for the last 6 years and I find that you can go in shorts and a light sweater gate opening , and a heavier top at night.. I usually wear crop pants or light weight cargo style pants.. (love the pockets) with hiking sandals.. and layer my tops.. I do have a hat and gloves in my bag and socks (told you I get cold) but the rest of my party only wear shorts and Tees. couple of years ago when we were leaving the hotel for the park.. it started raining.. I bought a light weight rain slicker .. and by the time we got to the hotel it had stopped.. but for my it was cool that day.. and yet another year , we ended up buying the water misters as it was sooooooo hot,... I dont think I wore my sweater at all during the days.. we even have a photo of me in a T Shirt... we still laugh at that.!!
it does get cooler at night of course... sun gone and tired bodies... but again to others not so bad that you are running for woolens , but cool enough for a heavier sweater... for me . thats when the hat and gloves come out and yes the socks with the sandals.. dorky I know.. but Im hoping no one will see in the dark lol
Your dates predict low 70's and if thats cold to you. then make sure you layer.. I would wear lighter pants of some kind that you can roll up during the warmer parts of the day and then roll back down later that night ..!!
Hope you have a great trip..