  This paper considers the temperature patch problem for the incompressible
Boussinesq system with no diffusion and viscosity in the whole space
$\mathbb{R}^2$. We prove that for initial patches with $W^{2,\infty}$ boundary
the curvature remains bounded for all time. The proof explores new
cancellations that allow us to bound $\nabla^2u$, even for those components
given by time dependent singular integrals with kernels with nonzero mean on
circles. In addition, we give a different proof of the $C^{1+\gamma}$
regularity result in [23], $0<\gamma<1$, using the scale of Sobolev spaces for
the velocity. Furthermore, taking advantage of the new cancellations, we go
beyond to show the persistence of regularity for $C^{2+\gamma}$ patches.
