Exactly - it can be everything between 60F to 90F. Raining, windy, sunny and humited. The only thing that is sure, is that there will not be any snow and it will not be freezing.
So a recommendation is to bring something light, so that you can easily put on several layers, and then take one or more layers off after your need. Waterproof rainbraker is always good - but also bring shorts and t-shirts - the weather can be good.