If forecasts show temperatures dipping into the lower 30’s, it’s best to go ahead and protect your plants while you can. If unsure of what is frost-tolerant, it is better to go ahead and cover or bring it indoors rather than risk it freezing. You can use a light sheet, a frost blanket or a tarp. Use something to hold down the sides so that the wind does not blow it away. Potted annual flowers should always be brought indoors or into the garage on cooler nights.