Annual dianthus can withstand minor frost without issue, but strong freezes can harm the plant. Dianthus can be grown as a winter annual when the winters are mild.
How cold can you go before dianthus dies?
Thermodynamics and Humidity These plants don’t enjoy a severe freeze but can endure a moderate frost. Cover plants with a frost blanket if the forecast calls for lows below 40 degrees Fahrenheit to protect them. In summers with continuously high temperatures above 85 degrees Fahrenheit, the blooms may also become dormant.