Is there a way to align this column on t_p?
\begin{center}
\begin{tabular}{cl}
$t_p \le -2\; ^\circ\mathrm{C},$ & frost is expected \\
$-2\; ^\circ\mathrm{C} \le\, t_p \le 2\; ^\circ\mathrm{C}$ & frost is possible \\
$t_p > 2\; ^\circ\mathrm{C}$ & frost is not expected
\end{tabular}
\end{center}
Added from wrong answer:
It is also possible to put every part of this as a separate column in a table:
\begin{tabular}{llllll}
& & $t_p$ & $\le$ & $\SI{-2}{\celsius}$ & frost is expected \\
$\SI{-2}{\celsius}$ & $\le$ & $t_p$ & $\le$ & $\SI{2}{\celsius}$ & frost is possible \\
& & $t_p$ & $>$ & $\SI{2}{\celsius}$ & frost is not expected
\end{tabular}
I do not know how to align the 2's in the 4th column, though.