I believe that the veil between the spirit plane and our plane is thin not only on Samhain but on Beltane also. Why you may ask yourself? Well, let me explain my theory and then decide for yourself if you agree or not.
Both Sabbats are fire festivals. Beltane for fertility and to bless the fields and livestock to produce a bountiful harvest and Samhain for celebrating the end of that bountiful harvest for the year.
As one is occurring in one hemisphere be it northern or southern, while the other is happening in the other one. So I feel the veil does not just thin out for one half of the planet it would be thin everywhere.
While one is celebrating Mother Earth waking up the other celebrates her going to sleep to restore herself.I
So what do you Beltane and Samhain may be two sides to the same coin or not?
May what you sow on Beltane give you a final bountiful harvest on Samhain!