Section 16H. Whenever the quantity of fresh milk available from registered dairy farms is, for each of three consecutive months, less than one hundred and thirty per cent of the quantity disposed of by licensed milk dealers as fluid milk within the commonwealth, the commissioner shall have the authority to approve the temporary receipt, by any licensed milk dealer applying therefor, of milk produced on unregistered dairy farms in such areas as he may approve; provided, that such milk shall not otherwise be exempted from compliance with the rules and regulations established pursuant to section thirteen; and provided, further, that the commissioner may authorize the inspection and registration of such farms under the provisions section sixteen C as may be necessary to assure a continued supply of fresh milk in the commonwealth at a level which shall not be less than one hundred and thirty per cent of the quantity of fluid milk disposed of within the commonwealth. Nothing in this section shall be construed as preventing the commissioner, for reasons involving the public health, from authorizing the temporary receipt from unregistered farms for such periods and in such volume as he may determine to be necessary.