How to Predict Early and Last Frost Dates

Knowing when the last frost in the spring or the first frost the fall is likely to occur makes gardening easy and lets you know when to plant or cover those tender vegetables and flowers.. Referring to the average frost date for your area gives you a good idea of when to expect a frost, but there are other ways to tell if a frost is likely to occur.

Lunar Calendar

Frost date charts

Plant protectors

Thermometer

Look for the full moon nearest the average last frost date for your area. Regardless of what the average last frost date is, frosts normally occur during or within two to three days of the full moon. In my area the expected last spring frost is for June 4th. This is the date where there is only a 10% chance of frost after the date.

Determine the date of the full moon closest to your expected last frost date. Although there are some who claim that the full moon has no affect on frost, many gardeners claim that a frost is most likely to occur during the full moon. My 20 years of gardening experience bares out this claim. In this case, we will look for the full moon closest to June 4th. This year, there is a full moon on June 7th. There is a high likelihood that there will be a frost sometime between June 7th and June 9th. Watch these dates carefully for any indication of approaching frost.

Listen to your weather reports closely for any sign that the temperatures will drop into the 30s. Weathermen often provide frost alerts that can be very helpful in determining if your garden will receive a frost. Keep in mind that low lying areas may create a frost pocket and you may get a frost when your neighbors do not. Gardens on hilltops may also get a frost before others. Frost may occur and injure your plants even if the temperatures remain above 32 degrees, as the surface of the soil may be cooler than the ambient temperature.

Observe the cloud cover. Clear skies are more likely to bring a frost than cloudy skies. The radiant heat from the sun that has been absorbed by the earth is released once the sun goes down. Clouds help to trap the heat close to the surface of the earth and may provide protection for your garden. Clear starry skies are likely to produce a frost as the rising heat from the earth is not contained.

Check for winds. High winds may actually cause plants to lose moisture making them more susceptible to frost, whereas a light breeze may prevent frost from settling. Dry still air may indicate a frost.

Water your plants on the day that a frost is expected, to provide additional protection. Although this may seem contradictory, the moisture in the soil will release into the air raising the humidity level and raising the dew point. Plants can withstand lower temperatures without being damaged by frost when the air is humid.

Cover plants with plant protectors or newspapers before the sun sets to hold in heat. Anchor the covers with rocks or sticks to prevent them from blowing off in the wind.

Follow the same process in late summer and early fall when you approach the average expected frost date. You can often get several weeks of growing weather after the first fall frost if you protect your plants.

Begin watching for signs of frost several days before the full moon.