To be exact.. it does effect... but negligible in our tank temperature (Depends how accurate u want ).... in general, ~0.0015 delta from 25°C to 30°C.. I suggest keep SG close to nominal ~1.022-1.023 for Hydrometer.. to handle SG fluctuation due to evaporation and measurement error from Hydrometer... If possible verify your hydrometer with reflectometer or pinpoint... u will found another ~0.001 SG offset...
Cheers and Happy Reefing....