Dry, arid mean devoid of moisture.
Dry may suggest freedom from noticeable moisture either as a characteristic or as a desirable state or it may suggest deficiency of moisture or the lack of normal or necessary moisture or, again, it may suggest exhaustion or dissipation of water or other liquid.
Arid implies destitution or deprivation of moisture and therefore extreme rather than relative dryness.
In its chief applications to regions or territory, it suggests waste or desert land.
In extended use, as applied to such matters as subjects, books, or sermons, dry suggests the lack of qualities which compel interest or attention.
Arid, on the other hand, connotes absence of all qualities which mark the thing so qualified as worthwhile, fruitful, or significant.
As applied to persons, their manner, or their words and expressions, dry implies a loss of normal or often of youthful human warmth, freshness, responsiveness, or enthusiasm; arid, an absence of these qualities or an incapacity for them.
Specifically, dry often suggests the repression of feeling for the sake of outwardly appearing aloof or imperturbed.
Arid, on the other hand, often connotes a deadening of feeling, especially as shown by a loss of fervor or hope.