Icing and environmental variations pose major challenges for structural health monitoring (SHM), as they can alter sensor responses in ways that resemble structural damage. Reliable damage identification therefore requires understanding how temperature, surface water, ice accretion, and operational loads influence SHM signals. This work investigates the environmental sensitivity of two SHM techniques, Electromechanical Impedance (EMI) and Guided Waves (GW), using piezoelectric transducers integrated on an aluminium plate and on a carbon-fibre reinforced polymer (CFRP) rotor blade. In the first campaign, controlled static tests were carried out on an aluminium plate inside a climate chamber, with temperatures varied from 20 °C to –40 °C under dry and iced conditions. EMI measurements showed systematic temperature-dependent shifts of impedance magnitude and resonance frequencies, while ice introduced additional spectral features linked to changes in boundary conditions. GW results revealed strong amplitude attenuation with decreasing temperature and further reduction under ice, whereas time-of-flight remained largely unchanged. To extend the investigation to realistic operating conditions, GW measurements were performed on a CFRP rotor blade in a spinning climate chamber. These measurements were conducted as a secondary task within a larger icing campaign, requiring the SHM system to be adapted to existing constraints and resulting in increased noise. Despite this, two robust GW features, peak amplitude and total signal power, were extracted across several operating states including water impingement, rotation up to 750 rpm, dynamic icing, and static iced conditions. Both features showed consistent qualitative sensitivity to temperature, rotation, water, and ice accretion. Overall, the combined experiments demonstrate that EMI and GW signals are significantly influenced by environmental and operational conditions, often to an extent comparable to structural damage. These findings emphasize the need for environmental compensation strategies to ensure reliable EMI- and GW-based damage detection and localization on aerostructures, and provide a foundation for future studies involving controlled damage scenarios.