  Two arguments have suggested the presence of subsurface water ice at
latitudes lower than 30\textdegree~on Mars. First, the absence of CO2 frost on
pole-facing slopes was explained by the presence of subsurface ice. Second,
models suggested that subsurface ice could be stable underneath these slopes.
We revisit these arguments with a new slope microclimate model. Our model shows
that below 30{\deg} latitude, slopes are warmer than previously estimated as
the air above is heated by warm surrounding plains. This additional heat
prevents the formation of CO2 and subsurface water ice for most slopes. Higher
than 30{\deg}S, our model suggests the presence of subsurface water ice. In
sparse cases (steep dusty slopes), subsurface ice may exist down to 25{\deg}S.
While hypothetical unstable ice deposits cannot be excluded by our model, our
results suggest that water ice is rarer than previously thought in the +-
30{\deg} latitude range considered for human exploration.
