A method of heating water on a continuous flow basis to be used in fracturing an oil and/or gas producing formation, comprising the steps of: a) providing a transportable heating apparatus for heating water to a temperature of at least 4.4 degrees C (40 degrees F); b) pumping a water stream of cool or cold water to a mixer comprising a tubular or cylindrically-shaped body with a bore, the cool or cold water stream being at a temperature of less than a predetermined target temperature; c) the mixer having a first inlet that receives cool or cold water from the stream of step "b" and a first outlet that enables discharge of a substantially continuous stream which is a mix of cool or cold and hot water, the bore communicating with the first inlet and the first outlet; d) the mixer having a second inlet that enables heated water to enter the bore of the tubular or cylindrically-shaped body of the mixer and a second outlet that enables cool or cold water to be removed from the bore of the tubular or cylindrically-shaped body of the mixer, wherein the first inlet is upstream of the second outlet, which is upstream of the second inlet, which is itself upstream of the first outlet; e) adding heated water from the transportable heating apparatus of step "a" to the mixer through a first flowline via the second inlet; f) removing cool or cold water from the mixer through the second outlet by way of a second flowline connecting the second outlet of the mixer to a vessel of the heating apparatus; g) wherein the volume of water of step "b" is greater than the volume of water of step "e"; h) connecting the mixer with a tank by way of a third flowline, and adding a selected proppant to the water discharged from the first outlet of the mixer using the tank; i) wherein water flows substantially continuously from the first inlet to the first outlet during the heating process; and j) transmitting the water and the proppant from the tank into an oil and/or gas producing formation through a fourth flowline; wherein the flow rate of the water stream in step "b" is adjusted to meet the required temperature for the water used in fracturing. a) providing a transportable heating apparatus for heating water to a temperature of at least 4.4 degrees C (40 degrees F); b) pumping a water stream of cool or cold water to a mixer comprising a tubular or cylindrically-shaped body with a bore, the cool or cold water stream being at a temperature of less than a predetermined target temperature; c) the mixer having a first inlet that receives cool or cold water from the stream of step "b" and a first outlet that enables discharge of a substantially continuous stream which is a mix of cool or cold and hot water, the bore communicating with the first inlet and the first outlet; d) the mixer having a second inlet that enables heated water to enter the bore of the tubular or cylindrically-shaped body of the mixer and a second outlet that enables cool or cold water to be removed from the bore of the tubular or cylindrically-shaped body of the mixer, wherein the first inlet is upstream of the second outlet, which is upstream of the second inlet, which is itself upstream of the first outlet; e) adding heated water from the transportable heating apparatus of step "a" to the mixer through a first flowline via the second inlet; f) removing cool or cold water from the mixer through the second outlet by way of a second flowline connecting the second outlet of the mixer to a vessel of the heating apparatus; g) wherein the volume of water of step "b" is greater than the volume of water of step "e"; h) connecting the mixer with a tank by way of a third flowline, and adding a selected proppant to the water discharged from the first outlet of the mixer using the tank; i) wherein water flows substantially continuously from the first inlet to the first outlet during the heating process; and j) transmitting the water and the proppant from the tank into an oil and/or gas producing formation through a fourth flowline;