Justification

In the interest of safety and reliability an "else" clause should always be included to be sure all possible cases are covered.

Example 1

if (temp < 0)
{
   /* any statement */
}
else if (temp > 0)
{
   /* any statement */
} /* WRONG */         

Example 2

if (temp < 0)
{
   /* any statement */
}
else if (temp > 0)
{
   /* any statement */
}
else /* temp == 0   */ /* RIGHT */
{
   /* Log an error */
}

Note

It is best practice to use the last "else" clause to log an error even (or especially) if one should never get there.