Multiple zeta values (MZVs) are real numbers defined by an infinite series, generalizing values of the Riemann zeta function at positive integers. Finite truncations of this series are called multiple harmonic sums and are known to have interesting arithmetic properties. When the truncation point is one less than a prime p, the modulo p values of multiple harmonic sums are called finite MZVs. This paper introduces a new class of congruence for multiple harmonic sums, which we call weighted congruences. These congruences can hold modulo arbitrarily large powers of p, and generalize the class of homogeneous relations for finite MZVs. Unlike results for finite MZVs, weighted congruences typically involve harmonic sums of multiple weights, which are multiplied by explicit powers of p depending on weight. We also introduce a class of p-adic series identities, which we call asymptotic relations, giving weighted congruences holding modulo arbitrarily large powers of p. We define a new truncated analogue of the multiple zeta function, and use it to give an algebraic framework for studying weighted congruences and asymptotic relations.