Silicon single crystal rods for semiconductors have mainly been manufactured by the Czochralski method, in which the quality of grown crystal rods is affected by the melt flow. In this study, experiments were carried out with a model system of the Czochralski melt under rotational horizontal magnetic fields. The temperature distribution in the melt was measured over a range of magnetic strengths and rotational rates of magnetic field. A pair of permanent magnets was used to generate the magnetic field, and a low rotational frequency (0.05-0.8 Hz) of the magnetic field was applied to the Czochralski melt. Asymmetric temperature distributions occur in the melt and rotate in the same direction as the crystal in the absence of a magnetic field or in a static horizontal magnetic field. Under a strong magnetic field or one rotating at a high rate, the temperature distributions rotate in the same direction as the magnetic field, even when this is opposite to the rotation of the crystal rod. The periodic temperature oscillation is caused by the rotation of the asymmetric temperature distribution in the melt. The oscillation period strongly depends on the rotational magnetic field.