First it was the rain...and now we are talking frost tonight. A Frost Advisory will go into effect late tonight through early tomorrow morning. You'll want to make sure you bring inside or cover any sensitive plants this evening.
We have the perfect setup for widespread frost develop for the area. An incoming high pressure system will arrive late today and will settle overhead by tomorrow. This brings with it drier air which helps to clear out the cloud cover this evening. Dry air also means low dew points, this typically brings colder overnight lows as low temperatures fall close to dew point temperatures. You also need light winds for frost development, because when winds are stronger it helps to mix out the colder air. When you have clear skies, then you have nothing to insulate heat near the surface, again helping low temperatures to fall to their lowest potential, the dew point.
You'll want to either bring in or cover any sensitive plants before you head to bed tonight. This evening isn't the only chilly night in the forecast, frost is possible again Saturday night into Sunday morning.