just water when you can, you cant choose when it rains and nature seems to have managed perfectly well for a few years now.
There are many pros and cons to the time you water if you care to get technical about it but the most important thing is making sure the plants get some when they need it.
One of the reasons why watering early morning is recommended is because the soil has cooled down. If we water in the evening on soil which is very warm, the water evaporates.