Hoar-frost

The grass was silvered with hoar-frost and in the wood across the stream a bird was singing.

Source: tatoeba (12015045)

And novv the mounting ſun diſpels the fog; / The rigid hoar-froſt melts before his beam; […]

Source: wiktionary

On Sunday night, January 23, ſeveral things vvere laid out at the Obſervatory, ſuch as ſheets of brovvn paper, pieces of boards, plates of metal, glaſſes of ſeveral kinds, &c. vvhich all began to contract hoar-froſt ſeemingly as ſoon as each body had time to cool dovvn to the temperature of the air. The ſheets of brovvn paper being ſo thin acquired it ſooneſt, and vvhen beheld in candle-light they became beautifully ſpangled over by innumerable reflections from the ſmall cryſtals of hoar-froſt vvhich had parted from the air.

Source: wiktionary

The mean temperature of the day and night at which injurious hoar-frosts may occur, may, relatively to the freezing-point, be very high.

Source: wiktionary