Due to intermolecular hydrogen bonding in alcohols, large energy is required to break these bonds, and thus alcohols have high boiling points.
The factors affecting the boiling/melting points of alcohols are hydrogen bonds and van der Waals dispersion forces, and dipole-dipole interactions. The hydrogen bonds and dipole-dipole interactions will remain relatively the same throughout the series of alcohols. However, the van der Waals dispersion forces increase as the length of the hydrocarbon chain increases. This is due to the increase in the number of electrons in the molecules, which increases the strength and size of the temporarily induced dipole-dipole attraction. Hence, more energy is required to overcome the intermolecular forces, increasing boiling/melting points.