A process to prepare an olefin from its corresponding alcohol is improved by reacting, under reaction conditions including a first temperature, an aliphatic alcohol and, optionally, diluent water, to form a reaction product including at least a dialkyl ether. The product is then reacted again, under higher temperature to complete the dehydration of the dialkyl ether to the desired olefin. This process is particularly suitable to prepare ethene from ethyl alcohol. The stepped temperature scheme serves to reduce the formation of byproduct aldehydes, which in turn reduces coke formation, fouling, and the need to handle large amounts of water, thereby lowering energy and capital costs.