  In recent years, there have been increasing experimental evidence suggesting
the existence of an electronic nematic state in a number of unconventional
$d$-wave superconductors. Interestingly, it is expected that the long-range
nematic order can coexist with $d$-wave superconductivity. We analyze the
in-plane upper critical field $H_{c2}$ after taking the influence of nematic
state into account, and find that the four-fold oscillation of angle-dependent
$H_{c2}$ in a pure $d$-wave superconducting state is turned into a novel
two-fold oscillation pattern by a weak nematic order. Moreover, such effect is
much more significant at higher temperatures. These behaviors are measurable
and may be used to probe the predicted coexisting nematic order in $d$-wave
superconductors. In addition, we show that the concrete angular dependence of
$H_{c2}$ and the positions of its maximum can be strongly affected by several
parameters, including temperature and $T_c$.
