[Unosolo]

spindritf, not necessarily, we don't know the initial temperature of the water and on a hot day (as per the problem statement) the ice-water system will be absorbing some of the external energy.

In practical world, more likely that water will start at around 20-25°C mark and will be considerably cooler once the ice has melted but still above 4°C. So the water volume is likely to shrink a tiny bit due to the rising density and then some more due to ice and water evaporation.

But the effect might be barely noticeable and for some time water will stay level with the edges after ice melted.