Frost Climatology
Frost forms when moisture on a surface is cooled below the dewpoint temperature, typically when the air temperature is between 33°F and 36°F and winds are light. Frost is not guaranteed if the air is dry or winds are above 8 miles per hour, even if the temperature is within this range. When the air temperature dips below 32°F, a freeze occurs that harms sensitive outdoor plants. A “hard freeze” occurs when the air temperature drops below 28°F for more than three consecutive hours, which kills seasonal vegetation and formally ends the growing season. Dates for the typical first and last frosts, freezes, and hard freezes are provided for select weather stations. Averages are based on 1991-2010 climate normals.
Fall Average and Record Dates
| Station | Location | Average First Frost | Earliest First Frost | Latest First Frost | Period of Record |
| Block Island State Airport* | New Shoreham | November 3 | October 5 (1965) | November 29 (1948) | 1948-1994 |
| Coventry 2 (COOP)** | Coventry | October 14 | September 21 (2020) | November 2 (2021) | 2017-2023 |
| Kingston - University of Rhode Island (COOP) | South Kingstown | September 27 | August 22 (1982) | October 24 (2021) | 1893-2024 |
| Newport Rose (COOP)** | Newport | October 31 | September 28 (1965) | November 11 (1994) | 1958-2003 |
| Newport State Airport | Middletown | October 20 | October 5 (1996) | November 8 (2014) | 1996-2024 |
| North Foster (COOP) | Foster | October 7 | September 18 (1990) | October 31 (2023) | 1975-2024 |
| R.I. T.F. Green Int'l Airport | Warwick | October 15 | September 21 (1956) | November 4 (1971) | 1932-2024 |
| Tiverton (COOP)** | Tiverton | October 23 | October 8 (1999) | November 9 (2005) | 1998-2018 |
| Westerly State Airport | Westerly | October 14 | September 21 (2020) | November 2 (2021) | 1999-2024 |
| Woonsocket (COOP) | Woonsocket | October 9 | September 17 (2002) | October 21 (2005) | 2004-2020 |
*Average derived from 1981-2010 climate normals.
**Weather station closed.
| Station | Location | Average First Freeze | Earliest First Freeze | Latest First Freeze | Period of Record |
| Block Island State Airport* | New Shoreham | November 12 | October 15 (1991) | December 3 (1985) | 1948-1994 |
| Coventry 2 (COOP)** | Coventry | October 25 | October 18 (2020) | November 4 (2021) | 2017-2023 |
| Kingston - University of Rhode Island (COOP) | South Kingstown | October 9 | September 10 (1938) | November 3 (1918) | 1893-2024 |
| Newport Rose (COOP)** | Newport | November 12 | October 18 (1985) | December 12 (1998) | 1958-2003 |
| Newport State Airport | Middletown | November 4 | October 19 (2001) | November 19 (2000) | 1996-2024 |
| North Foster (COOP) | Foster | October 16 | September 29 (2000) | November 8 (2017) | 1975-2024 |
| R.I. T.F. Green Int'l Airport | Warwick | October 28 | September 30 (1951) | November 19 (1935) | 1932-2024 |
| Tiverton (COOP)** | Tiverton | October 31 | October 13 (2012) | November 19 (2000) | 1998-2018 |
| Westerly State Airport | Westerly | October 22 | October 7 (1999) | November 9 (2017) | 1999-2024 |
| Woonsocket (COOP) | Woonsocket | October 19 | September 17 (2002) | November 9 (2017) | 2004-2020 |
*Average derived from 1981-2010 climate normals.
**Weather station closed.
| Station | Location | Average First Hard Freeze | Earliest First Hard Freeze | Latest First Hard Freeze | Period of Record |
| Block Island State Airport* | New Shoreham | November 24 | November 16 (1991) | December 18 (1950) | 1948-1994 |
| Coventry 2 (COOP)** | Coventry | November 5 | October 22 (2018) | November 15 (2022) | 2017-2023 |
| Kingston - University of Rhode Island (COOP) | South Kingstown | October 18 | September 20 (1993) | November 20 (2000) | 1893-2024 |
| Newport Rose (COOP)** | Newport | November 22 | October 24 (1969) | December 19 (1998) | 1958-2003 |
| Newport State Airport | Middletown | November 18 | October 25 (2003) | December 11 (2011) | 1996-2024 |
| North Foster (COOP) | Foster | October 28 | October 1 (1992) | December 2 (2011) | 1975-2024 |
| R.I. T.F. Green Int'l Airport | Warwick | November 9 | October 8 (1954) | December 7 (2009) | 1932-2024 |
| Tiverton (COOP)** | Tiverton | November 14 | November 2 (2008) | December 12 (1998) | 1998-2018 |
| Westerly State Airport | Westerly | November 3 | October 13 (2012) | November 28 (2016) | 1999-2024 |
| Woonsocket (COOP) | Woonsocket | October 28 | October 13 (2012) | November 15 (2014) | 2004-2020 |
*Average derived from 1981-2010 climate normals.
**Weather station now closed.
Spring Average and Record Dates
| Station | Location | Average Last Frost | Earliest Last Frost | Latest Last Frost | Period of Record |
| Block Island State Airport* | New Shoreham | April 23 | April 9 (1955) | May 27 (1972) | 1948-1994 |
| Coventry 2 (COOP)** | Coventry | May 7 | April 23 (2021) | May 21 (2020) | 2017-2023 |
| Kingston - University of Rhode Island (COOP) | South Kingstown | May 15 | April 26 (1924) | June 19 (1939) | 1893-2024 |
| Newport Rose (COOP)** | Newport | April 23 | April 12 (1999) | May 19 (1984) | 1958-2003 |
| Newport State Airport | Middletown | April 28 | April 11 (2019) | May 18 (2023) | 1996-2024 |
| North Foster (COOP) | Foster | May 9 | April 22 (1979) | June 1 (2009) | 1975-2024 |
| R.I. T.F. Green Int'l Airport | Warwick | April 28 | April 9 (1994) | May 27 (1972) | 1932-2024 |
| Tiverton (COOP)** | Tiverton | April 26 | April 17 (2004) | May 7 (2007) | 1998-2018 |
| Westerly State Airport | Westerly | May 4 | April 21 (2014) | May 19 (2003) | 1999-2024 |
| Woonsocket (COOP) | Woonsocket | May 6 | April 23 (2011) | May 16 (2000) | 2004-2020 |
*Average derived from 1981-2010 climate normals.
**Weather station closed.
| Station | Location | Average Last Freeze | Earliest Last Freeze | Latest Last Freeze | Period of Record |
| Block Island State Airport* | New Shoreham | April 6 | March 16 (1980) | April 30 (1992) | 1948-1994 |
| Coventry 2 (COOP)** | Coventry | April 18 | April 4 (2017) | May 10 (2020) | 2017-2023 |
| Kingston - University of Rhode Island (COOP) | South Kingstown | May 6 | April 12 (1921) | June 3 (1986) | 1893-2024 |
| Newport Rose (COOP)** | Newport | April 11 | March 25 (1998) | May 19 (1991) | 1958-2003 |
| Newport State Airport | Middletown | April 13 | March 28 (2010) | May 1 (2000) | 1996-2024 |
| North Foster (COOP) | Foster | April 28 | April 9 (2017) | May 19 (2002) | 1975-2024 |
| R.I. T.F. Green Int'l Airport | Warwick | April 12 | March 12 (1945) | May 9 (1956) | 1932-2024 |
| Tiverton (COOP)** | Tiverton | April 12 | March 20 (2000) | April 25 (2015) | 1998-2018 |
| Westerly State Airport | Westerly | April 21 | March 26 (2017) | May 18 (2013) | 1999-2024 |
| Woonsocket (COOP) | Woonsocket | April 25 | April 3 (2017) | May 13 (2005) | 2004-2020 |
*Average derived from 1981-2010 climate normals.
**Weather station closed.
| Station | Location | Average Last Hard Freeze | Earliest Last Hard Freeze | Latest Last Hard Freeze | Period of Record |
| Block Island State Airport* | New Shoreham | March 24 | March 1 (1973) | April 14 (1959) | 1948-1994 |
| Coventry 2 (COOP)** | Coventry | April 6 | March 25 (2017) | April 23 (2020) | 2017-2023 |
| Kingston - University of Rhode Island (COOP) | South Kingstown | April 22 | March 22 (1953) | May 19 (1944) | 1893-2024 |
| Newport Rose (COOP)** | Newport | March 29 | March 9 (1958) | May 6 (1991) | 1958-2003 |
| Newport State Airport | Middletown | March 30 | March 19 (2000) | April 11 (2018) | 1996-2024 |
| North Foster (COOP) | Foster | April 12 | March 25 (1998) | May 7 (2001) | 1975-2024 |
| R.I. T.F. Green Int'l Airport | Warwick | March 29 | February 27 (1942) | April 23 (1989) | 1932-2024 |
| Tiverton (COOP)** | Tiverton | April 1 | March 19 (2000) | April 18 (2014) | 1998-2018 |
| Westerly State Airport | Westerly | April 2 | March 2 (2020) | April 16 (2008) | 1999-2024 |
| Woonsocket (COOP) | Woonsocket | April 10 | March 28 (2010) | May 1 (2008) | 2004-2020 |
*Average derived from 1981-2010 climate normals.
**Weather station closed.
Frost Advisories and Freeze Warnings
The National Weather Service Boston, MA weather forecast office issues frost advisories and freeze warnings for Rhode Island between May 1 and October 11.
- Frost advisories are issued when the minimum shelter temperature is between 33°F and 36°F during the growing season.
- Freeze warnings are issued when the temperature drops below 32°F during the growing season.
Before May 1 and after October 11, farmers and gardeners are advised to follow the local temperature forecast and protect sensitive outdoor vegetation.
Frost and Mosquitoes
How does frost affect mosquitoes?
A hard frost, also known as a “black frost” or a “killing frost”, results in the internal freezing of vegetation unaccompanied by the protective formation of hoarfrost. In addition to plants, this also affects small insects like mosquitoes.
Mosquitoes become less active at temperatures below 58°F and become largely inactive when temperatures fall below 50°F. Until all of Rhode Island experiences a true hard frost (defined as three consecutive hours below 32°F) which kills adult mosquitoes, the risk of mosquito-borne disease remains.