It depends. The Hornet battery powered rechargeable air horn is not affected by temperature as it uses an electric motor to drive a compressor, so cold temperatures will have little or no effect on it.
Compressed gas, or aerosol air horns, will not gasify in cold temperatures, either not creating the required pressure to operate the mechanical trumpet at all, or the pressure will be so low that the sound will be greatly diminished to a quiet squeak.