Structural Health Monitoring using Lamb waves is based on the theory of elastic waves propagating in plates. Signal attenuation and mode conversion are used for damage detection. It is well known that the voltage amplitude from low-profile piezoceramic sensors used for inspection may change not only due to damage but also due to an inappropriate transducer coupling and temperature effects. The paper studies the effect of temperature on Lamb wave responses. The work involves a simple experiment in which two piezoelectric ceramics are bonded on an aluminium plate. The plate is exposed to various levels of temperature. A couple of simple features extracted from the Lamb wave responses are analysed to show the effect of the temperature changes. The plate was later subjected to damage and the series of tests and analysis repeated in order to give some comparison between the effects of damage and temperature change upon the responses. Several ways of how this problem can be circumvented using appropriate signal processing techniques are discussed.