How to Find Your First Frost Date

The first frost. The end of the outdoor garden season. It’s always a frantic time when that first frost alert comes through the weather service. Do you need to cover your delicate plants? Or is it going to be so cold you need to pick everything and hope they ripen indoors? So much to plan and do. What if you could figure out when your first frost is coming and plan accordingly? It may be the most important date to discover for your garden each year. Here are the keys to how to find your first frost date.

Why is First Frost so Important?

When you are planning your garden, all the talk is about the last frost in the spring for your area. How many weeks before last frost to start your plants? How soon should you put them out to make sure they won’t get nipped? If you miscalculate and put your delicate plants out too soon, there is a real risk that you could lose a large part of your harvest for the year, or at least have a significant setback. I remember one year where I lost every pepper plant and 90% of my tomatoes to a late spring freeze.

But there is a similar need to know when the first frost is coming in the fall. That way you can plan when to succession plant your veggies to make sure you get your last harvest in. Knowing when the first frost is predicted will allow you to prepare your garden by adding frost protection. You can also pot up delicate plants to move inside. Or harvest all your warm season veggies to allow them to ripen indoors. Being caught unaware by an early fall frost can significantly reduce your overall harvest. You need to know how to find your first frost date to prepare your garden properly.

How to Read the Chart or Table?

When talking about frost dates, the charts and tables are usually searchable by location. You enter or address or zip code and it gives you a range of dates. Of course, the average first frost date doesn’t tell you exactly when you will have frost in any given year. That’s where the statistics come in. The dates usually come with a percentage. So, for example, the 90% first frost date would tell you that in 90% or 9 out of 10 years the first frost would have happened by that date. A 10% first frost date would only happen that early in 1 out of 10 years. The average first frost date would tell you when the first frost is 5 out of 10 years.

When you’re researching the first frost date for your area, you need to decide how comfortable you want to be in the answer. Maybe you have some plants that are really important to you, that you don’t want to take any chances with. You might want to get those safely inside when there’s only a 10% chance that you could have a first frost. Or you want to leave your last few tomatoes on the vine as long as possible to get as much vine-ripened flavor as you can. If you don’t care if a few of them get nipped, penciling in the 90% date on your calendar for your final harvest of all the remaining fruits is reasonable. You can also factor in how the weather has been trending so far in a particular year. If it’s been a warm fall, you might be willing to risk hoping for a late first frost.

If you want an easy to use interactive list that uses 30% dates, check out the Old Farmer’s Alamanac site.

Next Steps

Once you have your dates, you need to make your plan. If you’re already in the danger zone (your first frost date is past), then your garden is living on borrowed time. Decide which plants are your first priority to protect. Can you bring some of them inside? Are there ways to protect your plants from frost with cold frames or hoop houses? Or are you ready to call it quits on your outdoor gardening season and harvest everything left on your plants? Start checking the forecast regularly. Sometimes if you can protect your plants through a quick cold snap, you can get a couple of weeks of extra harvest time before the cold really sets in.

If you have a little more time on the calendar, start planning your next steps for each phase of protection, transplantation, or harvesting. You could even consider planting some short season vegetables if you have enough days to get them to maturity. If you have plants that could handle a light frost but not a moderate or heavy freeze, monitor your forecast to make decisions about what to do next. Now that you know how to find your first frost date, you can take action as needed. Keep your eyes peeled for that weather alert and be ready to implement your plan!

Just starting your garden and wanting to plan in the spring? Check out my How Do You Know When to Plant post all about using your last frost date to schedule your seed starting. Enjoy!