When to plant in Rialto, CA

Planting dates worked out from Rialto's own frost records, not a generic zone chart.

Frost is rare in Rialto: in 12 of the last 23 springs there was none at all. Frost dates matter less here than heat, so the planting table below is left out.

Safe to plant out

Feb 24

1 year in 10 has a later frost

Average last frost

Jan 16

about a 50% chance of a later one

Average first fall frost

Dec 18

1 year in 10 by Nov 30

Frost-free days

346

median, 1991–2020

Station used: Redlands · 17.9 km away · station 430 m, town 383 m. How we match towns to stations

Rialto's weather over time

How the growing season has shifted here, year by year, from the station's own records.

Each year's last spring frostLong-term trend

See the data as a table

Year	Last spring frost
1899	Feb 7
1901	Feb 11
1902	Jan 31
1903	Feb 17
1904	Feb 9
1905	Feb 14
1906	Apr 2
1907	Feb 27
1908	Feb 14
1909	Mar 12
1910	Feb 18
1911	Feb 28
1912	Feb 26
1913	Mar 25
1915	Feb 21
1916	Jan 13
1917	Mar 16
1918	Feb 19
1919	Feb 26
1920	Mar 27
1921	Apr 14
1922	Apr 6
1923	Mar 5
1924	Mar 22
1925	Jan 17
1926	Jan 28
1927	Jan 25
1928	Jan 24
1929	Apr 7
1930	Jan 8
1931	Feb 21
1932	Feb 19
1933	Mar 24
1934	Jan 9
1935	Mar 10
1936	Mar 27
1937	Feb 27
1938	Feb 17
1939	Mar 4
1940	Mar 13
1942	Feb 15
1943	Feb 10
1944	Mar 15
1945	Mar 1
1946	Mar 14
1947	Jan 30
1948	Mar 5
1949	Feb 15
1950	Feb 1
1951	Feb 28
1952	Mar 9
1953	Apr 10
1954	Mar 16
1955	Feb 24
1956	Mar 13
1957	Feb 1
1958	Mar 3
1959	Feb 9
1960	Jan 18
1962	Mar 14
1963	Mar 18
1964	Feb 27
1965	Feb 12
1966	Mar 4
1967	Jan 8
1968	Jan 30
1969	Feb 1
1970	Jan 29
1971	Feb 27
1972	Feb 3
1974	Mar 4
1975	Feb 18
1976	Mar 7
1977	Jan 10
1979	Feb 4
1981	Feb 5
1982	Mar 20
1983	Jan 21
1985	Mar 3
1987	Feb 27
1989	Feb 7
1990	Mar 13
1993	Jan 4
1996	Feb 27
1998	Jan 6
1999	Feb 12
2001	Jan 17
2002	Feb 1
2004	Jan 4
2007	Mar 1
2009	Feb 11
2011	Feb 27
2013	Feb 12

Each year's frost-free daysLong-term trend

See the data as a table

Year	Frost-free days
1899	326
1900	355
1901	303
1902	296
1903	316
1905	279
1906	230
1907	267
1908	282
1909	266
1910	315
1911	255
1912	282
1913	280
1914	345
1915	265
1916	303
1917	289
1918	306
1919	273
1920	243
1921	217
1922	211
1923	291
1924	270
1925	331
1926	319
1927	317
1928	298
1929	267
1930	314
1931	267
1932	294
1933	249
1934	327
1935	238
1936	277
1937	300
1938	267
1939	297
1940	276
1941	321
1942	318
1943	323
1944	289
1945	283
1946	291
1947	296
1948	274
1949	298
1950	332
1951	280
1952	260
1953	222
1954	286
1955	294
1956	252
1957	301
1958	258
1959	324
1960	323
1961	345
1962	285
1963	268
1964	259
1965	308
1966	297
1967	338
1968	321
1969	328
1970	327
1971	244
1972	304
1973	327
1974	294
1978	339
1979	289
1980	320
1981	320
1982	231
1983	304
1984	347
1985	281
1987	290
1989	307
1990	282
1991	363
1992	352
1993	360
1994	322
1995	363
1998	334
1999	321
2000	363
2001	347
2002	320
2003	348
2004	329
2005	363
2007	295
2008	346
2009	299
2010	328
2011	281
2012	352
2013	299
2014	363

Each year's average temperature, April to SeptemberLong-term trend

See the data as a table

Year	Growing-season temperature
1898	22.3 °C
1899	21.4 °C
1900	20.3 °C
1905	20.4 °C
1906	21.1 °C
1907	20.1 °C
1908	21.2 °C
1909	21.0 °C
1910	22.0 °C
1911	20.5 °C
1912	19.7 °C
1913	20.5 °C
1914	20.4 °C
1915	20.4 °C
1916	20.5 °C
1917	21.1 °C
1918	21.3 °C
1919	21.5 °C
1920	20.6 °C
1921	20.2 °C
1922	21.3 °C
1923	20.4 °C
1924	20.8 °C
1925	21.0 °C
1926	21.6 °C
1927	21.3 °C
1928	21.6 °C
1929	21.6 °C
1930	20.6 °C
1931	22.2 °C
1932	20.0 °C
1933	19.5 °C
1934	21.6 °C
1935	21.1 °C
1936	21.8 °C
1937	21.7 °C
1938	20.9 °C
1939	21.2 °C
1940	21.0 °C
1941	19.9 °C
1942	20.7 °C
1943	21.2 °C
1944	19.5 °C
1945	20.6 °C
1946	21.7 °C
1947	21.4 °C
1948	20.3 °C
1949	21.3 °C
1950	20.5 °C
1951	20.6 °C
1952	21.2 °C
1953	19.7 °C
1954	20.3 °C
1955	21.0 °C
1956	21.3 °C
1957	22.0 °C
1958	22.7 °C
1959	23.1 °C
1960	23.4 °C
1961	22.5 °C
1962	22.3 °C
1963	21.5 °C
1964	21.4 °C
1965	20.8 °C
1966	22.6 °C
1967	21.5 °C
1968	21.7 °C
1969	22.0 °C
1970	21.8 °C
1971	21.4 °C
1972	22.1 °C
1973	20.9 °C
1974	21.9 °C
1976	21.0 °C
1977	21.8 °C
1978	22.5 °C
1979	22.6 °C
1980	21.3 °C
1981	22.9 °C
1982	20.6 °C
1983	21.9 °C
1984	24.4 °C
1985	22.7 °C
1987	22.7 °C
1989	22.8 °C
1990	22.9 °C
1991	21.6 °C
1992	23.6 °C
1993	22.6 °C
1994	22.4 °C
1995	21.8 °C
1996	23.5 °C
1997	23.0 °C
1998	21.9 °C
1999	21.0 °C
2000	23.1 °C
2001	22.4 °C
2002	22.6 °C
2003	22.9 °C
2004	22.9 °C
2007	23.0 °C
2008	23.2 °C
2009	22.8 °C
2010	21.4 °C
2011	22.4 °C
2012	24.0 °C
2013	23.0 °C
2014	23.3 °C

What this means for you: Since 1899, Rialto's last spring frost has come about 2 days earlier per decade, on average. The frost-free season has grown by about 5 days per decade. Year-to-year swings are large, so keep using the safe date rather than the trend.

Source: daily records from Redlands (NOAA GHCN-Daily). Years with too many missing days are left out.

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