  Subsurface convection zones are ubiquitous in early-type stars. Driven by
narrow opacity peaks, these thin convective regions transport little heat but
play an important role in setting the magnetic properties and surface
variability of stars. Here we demonstrate that these convection zones are
\emph{not} present in as wide a range of stars as previously believed. In
particular, there are regions which 1D stellar evolution models report to be
convectively unstable but which fall below the critical Rayleigh number for
onset of convection. For sub-solar metallicity this opens up a \emph{stability
window} in which there are no subsurface convection zones. For LMC metallicity
this surface stability region extends roughly between $8M_\odot$ and
$16M_\odot$, increasing to $8M_\odot$ -- $35M_\odot$ for SMC metallicity. Such
windows are then an excellent target for probing the relative influence of
subsurface convection and other sources of photometric variability in massive
stars.
