I have heard the phrase "isolated rain" a lot on weather report over radio.
However, I don't know what it really means.
Could you reach out your helping hand?
When I hear "isolated rain showers" in the weather forecast, I think it means that there are smaller rain clouds, detached from one another, coming through the area. So a rain shower can show up at any time.
There may be several of these separate rains showers throughout the day. They don't last long.
This is different from an overcast or rainly day forecast.
The idea is that not all listeners will see rain, but some will. You also may hear of "scattered showers." I think isolated means even less of a chance of rain than scattered.