Thank you for reaching out to us. Several points here. First, the thermometer at the house probably not necessarily reflects the air temperature in your field. If it’s 36 degree at your house, it might only be 34 in the field, and most likely around 32 at plant-level. So now, an air temperature itself of 32 does not harm the flowers, but as you correctly stated, it’s the frost which can build on the flowers which will cause damage.
The dew point describes the temperature at which the air is saturated with water and morning condensation (dew) will start forming on surfaces (such as flowers). The colder the air, the less water it can hold. So the forming of dew is related to the amount of water in the air (humidity) and temperature. Dew always forms if the air temperature reaches the dew point.
Dew usually forms close to the surface, since this usually is the coldest area. That can be different if there is a lot of wind (more than 6-10 mph), because colder air can move in.
However, under low winds, and colder nights, especially when the soil is saturated, it’s very likely to experience dew in the morning.
Frost builds up when the air-temperature reaches a dew-point below freezing. That can happen gradually over night, with dew is building on the plants in a liquid phase, which then freezes over night (frozen dew). Or ice can directly deposit on the plant out of the vapor phase in the air (white frost, hoar frost).
So if your minimum temperature is predicted to be 40, your dew-point 34, you most likely don’t see frost over night. But if your minimum temperature is predicted to be 34, and your dew point is 25, there is a good chance that you will see frost over night!
In your case, I would recommend to measure temperatures directly in your field, maybe with an affordable weather station and use our weather forecasts to see what the general differences between min air temp. and dew point are in your area.
I hope that makes sense,