The melting kinetics of three-dimensional colloidal crystals consisting of poly(N-isopropylacrylamide) microgels was investigated by using UV-visible transmission spectroscopy. It was found that the melting was initiated with a decrease of the interplanar spacing of the crystals and that crystallites broke into smaller pieces at large overheating temperatures. The crystallites reach a minimum burst size before completely broken apart. The complete melting occurs as the average thermal fluctuation of the particles reach around 19%. The experimental results corroborate with recent computer simulations that conciliate the Lindemann criterion of melting with Born's mechanical instability.