Strawberry flowers are relatively resistant to frost damage while they are still in tight bud. Buds that are just about to open, and particularly open flowers, are more susceptible to damage.
The amount of damage that occurs will depend on the degree of frost and the length of time for which plants are exposed to it, but also on the relative position of flowers on the plant. Flowers covered by leaves, for example, will be less susceptible than those that are fully exposed.
Even strawberry flowers under cloches or polythene can be damaged; those close to or touching the polythene or glass are most at risk.