Its well established if you want to catch large fish from the surf that it can only be done at night, right? Only a fool would go it by day.

Surprising or not, many large shore fish are taken by day every year. I have a couple well over the 40# mark taken under blue bird conditions from the daytime surf.
Lets define large fish as well as daytime conditions before the question is posed.
Daytime=if there is any natural light present.This time of year it would be 4:30 am to 9:30 pm and would adjust accordingly as daylight increases or decreases.
Large fish=Don't want to insult anyone, so lets call a large 20# or better.
Question:
If you decide to go it by day from the surf for large fish, what types of conditons need to be present for you to fish with confidence? Do your day versus night methods differ at all, and if so,how?