Question

Cold water kept in an open container become warm on a hot summer afternion

Answer 1

This is due to transfer of heat.
Heat transfer from lower temperature to higher temperature.
And also it transfer heat upto temperature the when temperature of water become equal to
Atmospheric temperature of the summer hot afternoon.
So Cold water kept in an open container become warm on a hot summer afternoon

Answer 2

Answer:

because the sorroundings are warm

I am not sure