Gardeners often pay attention to their area’s first and last frost dates. They help determine when you should plant seeds or transplant starts, especially those sensitive to cool temperatures, and how long of a growing season you have. The Farmer’s Almanac has always been the go-to source for this information, which is how we learned that our average last frost date is May 15 and the average first frost is October 7. With the garden being done for the year, something I’ve been pondering is how accurate these dates are.

Mathematically, these averages are correct. Farmer’s Almanac and other sources likely use the same data I found from NOAA, which has historical data for their weather stations. With that data, it’s pretty easy to determine the average across a set of numbers. What I wanted to know is how often the first frost occurs before October 7 and the last frost after May 15.

For my purposes, I used a threshold of 35 degrees Fahrenheit. While people usually think of frosts occurring at 32 degrees Fahrenheit, tissue damage in plants can happen a few degrees warmer. Plus, the temperature is often lower at the ground than what the weather stations show. Here is a table with the results:

Year	Last Frost	Temp (F)	First Frost	Temp (F)
2025	Jun-3	34	Sep-9	35
2024	May-12	35	Oct-11	33
2023	May-18	35	Oct-10	33
2022	May-8	33	Oct-9	31
2021	May-15	33	Oct-19	34
2020	May-14	28	Sep-19	32
2019	May-16	33	Oct-13	33
2018	May-2	30	Oct-14	35
2017	May-16	34	Oct-1	32
2016	May-16	32	Oct-10	35
2015	May-15	35	Oct-18	32
2014	May-19	35	Oct-26	30
2013	May-27	35	Sep-25	35
2012	May-18	35	Oct-8	32
2011	May-10	34	Oct-23	33
2010	May-10	29	Oct-12	33
2009	May-19	31	Oct-6	35
2008	May-23	34	Oct-4	35
2007	May-13	35	Oct-27	35
2006	May-23	32	Oct-12	33
2005	May-9	34	Oct-28	33
2004	May-5	35	Oct-4	34
2003	Apr-26	30	Oct-2	30
2002	May-22	29	Oct-7	34
2001	May-31	35	Oct-7	31
2000	May-16	35	Sep-28	30

Takeaways

• In the past 25 years, the last frost of the spring occurred after May 15 on 14 occasions. It occurred before that date 10 times. It also fell perfectly on May 15 twice.
• The first frost of the fall took place after October 7 in 14 years and before October 7 on 9 occasions. It happened on October 7 twice.
• The last frost of spring had a temperature at or below freezing (32) 8 times, while the first frost of fall was below that threshold in 9 years. Most recently, those occurred in October 2022 and May 2020.
• The coldest temperature for the first frost was 30 degrees in 2000, 2003, and 2014. For the last frost it was 28 in 2020.
• This year has been one of the weirdest in recent memory. The last frost was on June 3, and the first frost was on September 9.

After tracking each year’s data since 2000, I looked at some outliers dating back to 1949, the first year that temperature data was recorded for this weather station.

• The latest last frost of the spring occurred on June 26, 1979, while the earliest last frost was on April 28, 1953. The temperature was 35 degrees both times. The April 28 date is actually later than the earliest last frost recorded in the table above, which took place on April 26, 2003.
• The earliest first frost of the fall occurred on August 15, 1963, when the temperature dipped to 34 degrees. The latest first frost was on October 22, 1962. It was 35 degrees that day. August 15 is much earlier than any of the past 25 years; however, we had a first frost later than October 22 five times since 2000.

What Can We Learn?

Beyond the obvious realization that the average first and last frost dates for your area are mathematically accurate, there’s only so much importance that should be placed on them. It’s good to know when the averages are, but I think they should be treated as rough estimates rather than set in stone specific dates. Each year brings temperatures and growing conditions, so it’s important to be flexible. This past spring, we had to wait until late June to plant some things because of how wet and cool it was. You can typically get a feel for how spring is going to go early in the year and can get a read on if the average start date will be accurate that year.

I loved looking at this data, and it was fun to remember why primary sources were so much fun to work with when performing historical research. After I wrapped up looking at this data, I started tinkering with precipitation data, specifically first and last snowfall dates, and may look into that more as a fun side project. In general, NOAA’s historical climate data will be something I regularly visit. Did you find this information interesting? Have you found that your area’s first and last frost average frost dates hold true on an annual basis?