How to Use First and Last Frost Dates to Plan Your Seed Starting Schedule

Summary

Vegetable and flower seed starting and planting schedule for Zone 6

Garden planning and preparation, seed sowing and starting… with gardening, timing is everything, and knowing how many weeks you are before the first and last frost dates is important in determining when to start your seeds indoors, sow seeds outdoors, and transplant seedlings outside. Even so, the dates are averages and can vary depending on the weather on any given year. Watch the weather reports closely when preparing to plant outdoors.

Know your garden zone and your first and last frost dates.

This seed starting calendar below is set up for plant hardiness zone 6 but can be adapted to your zone. To calculate when it is time to start your seeds and when to move your plants outdoors, you will need to know the first and last frost dates for your area and the length of your growing season. You can find this information by entering your zip code at plantmaps.com .

More detailed information on freeze and frost dates with temperature ranges can be found on garden.org.

Knowing the dates for your zipcode is helpful because even a few miles can change the local environment significantly.

For my area in the suburbs west of Cleveland, Ohio:

The average last frost is between May 1st and May 10th.
The average first frost is between October 20th and November 1st.
The frost-free growing season is around 170 days.

Last Frost Date (Cleveland, Ohio)

°F	90%	50%	10%
36°	Apr 25	May 11	May 27
32°	Apr 18	Apr 30	May 12
28°	Apr 4	Apr 16	Apr 29

First Frost Date (Cleveland, Ohio)

°F	10%	50%	90%
36°	Sep 25	Oct 7	Oct 18
32°	Oct 6	Oct 20	Nov 3
28°	Oct 23	Nov 4	Nov 15

*Data provided by the National Centers for Environmental Information.

Recent Last Frost Dates and Temperatures

The frost dates are not a guarantee, they are an average. For my area, there is a 50% chance that the last frost will be by April 30^th, and a 10% chance that the last frost will happen as late as May 15^th. By way of example, here are the last freeze dates and the lows on that date here in my suburb of Cleveland for recent years. From these results I can tell that I’m fairly safe if I plant things out any time in May, provided I am prepared to provide protection to my plants just in case. I will note that while these were the last frost days, there were in many of these years more than a few nights even in early May in that came close, with lows reaching 34 degrees.

Temperatures shown in Fahrenheit.

2021 – while much of April was warm, we had 7 inches of wet snow on April 21^st,a low of 31 degrees on April 22^nd, and a light frost with a low of 37 on April 30^th. On May 9th we had 35 degrees with brief period of sleet and freezing rain, and on May 10th it hit a low of 34 degrees.
2020 – a low of 30 degrees on May 9^th and 32 degrees on May 12^th
2019 – an amazingly early April 2^nd with a low of 32 degrees
2018 – April 29^th at 30 degrees.
2017 – April 8^th: 30 degrees.
2016 – April 10^th – 23 degrees.
2015 – April 24^th – 28 degrees.
2014 – April 15^th – 25 degrees
2013 – April 26^th – 30 degrees
2012 – April 29^th – 28 degrees
2011 – April 3^rd – 32 degrees
2010 – April 10^th – 32 degrees

When determining the best dates for seed starting and transplanting out for your area, consider your local growing conditions. For Ohio the recommendations for planting some seeds or transplants outside can read “as soon as the ground can be worked, in March or April”. It’s possible that the ground can be worked in March in other parts of Ohio, but here in my backyard it’s still cold and muddy, so I usually don’t start planting anything until April.

With a 50% chance that the last 32-degree day is at the end of April and a 90% chance that there will be no more frosts by May 12th, I stagger my plant-out days, with more cold tolerant varieties hardened off and planted outside in late April and early May and waiting to plant the fussier plants like tomatoes and peppers until mid-May. This also benefits the tender plants, as the ground is warmer by that time.

First Frost Dates and Your Growing Season

The number of days between the first and last frost dates is the length of your growing season. This helps in deciding what you can grow that will ripen and be ready for harvest before the first frost in the fall, as well as the best time for fall planting. It also helps for planning when to start your fall season crops, as some vegetables are best started late so that they don’t bolt during the hottest days of summer.