  We investigate an effective model for the finite temperature restoration
phase transition of the electroweak theory. It is obtained by dimensional
reduction of the $3+1$ dimensional full theory and by subsequent integration
over all static gauge degrees of freedom. The resulting theory corresponds to a
$3$-dimensional $O(4)$ ferromagnet containing cubic and quartic terms of the
field in its potential function. Possible nonperturbative effects of a magnetic
screening mass are parametrically included in the potential. We analyse the
theory using mean field and numerical Monte Carlo (MC) simulation methods. At
the value of the physical Higgs mass, $m_H=37~{\rm GeV}$, considered in the
present investigation, we find a discontinuous symmetry restoring phase
transition. We determine the critical temperature, order parameter jump,
interface tension and latent heat characteristics of the transition. The Monte
Carlo results indicate a somewhat weaker first order phase transition as
compared to the mean field treatment, demonstrating that non-perturbative
fluctuations of the Higgs field are relevant. This effect is especially
important for the interface tension. Any observation of hard first order
transition could result only from non-perturbative effects related to the gauge
degrees of freedom.
