The transition energies and the oscillator strengths of both the ultraviolet and visible series of the helium atom have been calculated in a hot, weak coupling plasma environment, modeled in terms of the Yukawa potential. Our approach, based on the full configuration interaction method, is found to be superior to those based on the atomic many-body perturbation theory, for it converges smoothly to accurate vacuum values as the screening parameter approaches to zero and also behaves smoothly with respect to increasing screening. Thus, it could be useful for plasma diagnostic purposes.