nullptr and pointer arithmetic

Considering the following code, is it safe to do pointer arithmetic on nullptr? I assume adding any offsets to a nullptr result in another nullptr, so far MSVC produce results as I expected, however I am abit unsure about whether using nullptr like this is safe:

float * x=nullptr;

float * y=x+31;//I assume y is a nullptr after this assigment

if (y!=nullptr)
{
/* do something */
}