In a perfect world, I'd always water early in the morning, but it just doesn't work out that way for me.
I've almost always watered after 4pm - for years - and never had any problems with it. I've never had a fungal issue. Probably the worst thing I've faced is that wind can be more active later in the day so it can blow the water around a bit more than if I were to water early in the day.
I have always followed the old adage not to water past 8pm though

.
Tom Maccubin is a great resource for dispelling gardening myths

. His book "The Perfect Florida Lawn" is really good:
Tom MacCubbin -- OrlandoSentinel.com
Amazon.com: Tom MacCubbin: Books, Biography, Blog, Audiobooks, Kindle