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First and Last Frost Dates
Enter your ZIP code, city, or state below to find the average first and last frost date in spring and fall in your area:
What are Frost Dates? Frost dates are the day of the year when it is calculated to be 50% likely that the temperature will dip below freezing, resulting in frost on the ground.
In spring, we have a ‘last frost date’, and in the fall we have a ‘first frost date’. These dates vary depending on various factors like latitude and longitude, altitude, and weather patterns that change yearly. It is hard to pinpoint an exact date so it is wise to assume that freezing temperatures are possible two weeks before the first frost date and two weeks after the last.
The dates in-between the last and first frost dates are days when it is safe to plant and when you should harvest your last vegetables of the season.
It is difficult to estimate when you will experience the first or last frost of the year without using data gathered over many years by the USDA and NOAA (which we use in our tool above).
Why is it important to know your frost dates as a gardener? When temperatures drop to a range of 29-30 degrees Fahrenheit, a ‘light freeze’ will damage delicate plants. A ‘moderate freeze’ will damage most plants in your garden except the hardiest, and it occurs with temperatures between 25-28 degrees Fahrenheit. A ‘severe freeze’ is almost always fatal to all garden plants, and it occurs when temperatures are lower than 24 degrees Fahrenheit. As a gardener who worked so hard on your beautiful garden, it is important to know when you need to take steps to preserve perennials and harvest annuals so the cold weather will not destroy them.
Frost dates data will also tell you when you need to start seeds and help you choose the correct plants for your area that will grow best under the temperature conditions you experience.
If you plant in succession, frost dates become more important because you will need to start your first garden as early as possible.
Which plants can/can’t stand the freeze? Some plants are so hardy that they will not be harmed by a light or moderate freeze, so you can start these varieties as early as possible and leave them in the ground as late as possible. Peas, onions, and spinach are the hardiest so you can plant them as soon as the soil in your garden is soft enough to begin working with.
Slightly less hardy varieties that will thrive when planted a week or two before the last frost of the season include kale, mint, broccoli, cabbage, beets, carrots, dill, radishes, cilantro, celery, potatoes, and lettuce.
Varieties that require transplanting, meaning that the seeds need to be started indoors before moving them to the garden, are very susceptible to frost damage, so it is imperative to wait to transplant them until there is no longer any danger of the temperature dropping below freezing. These include squash, tomatoes, cucumbers, pumpkins, peppers, basil, corn, beans, melons, and eggplants. How to Find Your Frost Dates There are two ways to find out the frost dates in your area, we’ll talk both methods along with the pros and cons.
1. The USDA Hardiness Zone Method To find the average frost dates for your region, you first need to determine your hardiness zone or planting zone. You can do this by using our planting zone map tool. Click on your state to zoom in or enter your zip code to find the zone number of your specific area.
Frost dates can vary widely within each state and county so it is important to find the correct zone for exactly where you will be planting. Then, you can use this handy list to check the first and last frost dates for your zone.
As an extra precaution, it is a good idea to assume a difference of two weeks from scheduled frost dates so that you are not caught off-guard. This means acting under the assumption that the last frost date of the spring will happen two weeks later than calculated, and the first frost date of the fall will happen two weeks earlier than the estimate. 2. The NOAA Climate Station Method Using the hardiness zone is the simplified method to find your frost dates. It is easy to use, but it can be less accurate.
Which is why to get more accurate dates with wider probabilistic ranges, you can use our tool that consolidates information from NOAA’s National Centers for Environmental Information (NCEI). All you need to do is enter your zip code on top of this page and it will locate your area and tell you the estimated first and last frost dates.
Scroll down further to find two tables, each giving the estimated dates for 90%, 50%, and 10% chance of frost before the first frost date or after the last frost date of the year. You can use these more specific ranges to maximize your gardening time during the year by pushing your planting earlier and your harvesting later.
This is the method we recommend you to use. The Limitations of Frost Dates It is important to remember that these dates are simply estimates and cannot account for unusual weather events. For instance, an abnormally warm spell during the cold season or a sudden onset of cold before the estimated first frost date will cause damage to certain plants, so you need to pay attention to weather warnings to make sure you are able to mitigate the damage.
Microclimates are also difficult to account for, which can be created by many different factors including large areas of concrete or steep changes in elevation. These variances within a certain zone mean that the frost dates in these areas will be slightly different from a nearby area in the same zone. This means that aside from taking note of frost dates, you need to research your area and take note of unique atmospheric changes affecting your plants over time.
Similarly, plants react to a variety of factors other than temperatures, such as light, humidity, soil type, and the duration of certain temperatures. It is vital to plant different varieties in areas of your garden that are best suited to them and make sure that your soil is adequately prepared and fertilized to support your plants.
Temperature fluctuations cause changes to the soil’s humidity which means that you need to adjust the balance of your soil when you notice sudden temperature shifts. Use these frost dates as a guideline but make sure to observe the weather, talk with your neighbors, and track the reaction of your plants through the year to make the most accurate decisions that will ensure the highest yield each harvest.
It is also important to trust your gut when it comes to your garden. If you are an experienced gardener, you know what works well in your soil and what does not, so stick with the methods you have been having success with. Your garden is its own microclimate since it is uniquely built. If it is more covered and contained than your neighbors yard, your plants will enjoy more warmth for longer, meaning you can push your luck by planting earlier and harvesting later.
What will you grow this winter? Why? Which garden zone are you in?
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