The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
0 /0 GULF COAST RESEARCH AND EDUCATION CENTER
IFAS, UNIVERSITY OF FLORIDA
5007 60th Street East
Bradenton, FL 34203
Bradenton GCREC Research Report BRA1990-10 April 1990
FREEZE PROBABILITIES IN MANATEE COUNTY
C. D. Stanley and D. N. Maynard'
Several devastating freezes have adversely affected the horticultural industries of
Florida during the 1980's. Vegetable, citrus, and ornamental crop growers have
suffered enormous direct monetary losses, unstable markets for a period after the
freeze, and perhaps loss of markets.
Although all horticultural enterprises are influenced by freeze occurrences, the
focus of this report is on freeze probabilities as relatedito vegetable production.
Because of the likelihood of freezes"in late Decenireiland early January, west
central Florida production of tender vegetables isqenteredion a fall and a spring
season, thereby avoiding the period of highlist freeze probability. In addition,
cropping periods are influenced by summer iairigat tie0nd of the spring season and
beginning of the fall season. Lastly, croppiig-..periods are controlled by the
production and marketing limitations associated with the north to south fall and
south to north spring progression of peninsular Florida.
Freeze probabilities at various Florida locations have been published previously
(2), but Bradenton data were not included in that report. Tampa was the only west
coast location reported for the 30-year period, 1941-1970. More recently (1),
climatic data on six Florida urban centers, including Ft. Myers, in relation to energy
conservation was published.
The object of this report is to provide vegetable growers in west central Florida
with information on freeze probabilities for use in scheduling production of tender
Materials and Methods
Freeze probabilities were calculated from weather data collected from 1954
through 1989 (5). Data were collected at 0800 daily using a weather shelter
containing standard maximum and minimum thermometers. Data were collected at
this location from 1965 through 1989, and, prior to that, at the previous Gulf Coast
Experiment Station location at what was 1300 9th Street East, Bradenton, Florida.
Although frosts and freezes are distinctly different climatological events, freeze is
used in this report to denote temperatures of 320F or below.
'Associate Professor of Soil Science and Professor of Vegetable Crops.
The earliest fall freeze was on 16 November 1969 and the latest spring freeze
was on 4 March 1980 during the 36-year recording period. Freeze probabilities for
two-week periods beginning
on 16 November and ending
on March 1 are shown in
Figure 1. The highest freeze
probability 46% occurs
during the last two weeks of
January. There is slightly
S "less probability 40%
during the first two weeks of
January. Freeze probabilities
of just over 30% occurred
during the last two weeks of
December and just under
S Wl O Is. i ftI 30% during the first two
i..," "J" weeks of February. A freeze
probability of 20% occurred
during the first two weeks of
Figure 1. Freeze probability at the GCREC, Bradenton, FL, during December and during the
two-week intervals beginning 16 November for the 36-year last two weeks of February.
period from 1954-1989.
period from 1954-1. Freeze probabilities of less
than 10% occurred during
the last two weeks of November and first two weeks of March.
increase as the winter season
progresses (Figure 2) from
8% by 1 December to 91%
by 15 February and remains
constant through 15 March.
This means that for fall
crops, there is a probability
of a freeze in 10 years out of
116 by 1 December and a
probability of a freeze by 15
December in 10 out of 35
years. Therefore, growers
run an increasing risk of crop
loss by freezes if harvest of
tender crops is extended into
The probability of a
freeze sometime during the
winter season decreases as
.1 i ~
* I. I
-- JI '
Figure 2. Probability of a freeze event occurring prior to the indicated date
at the GCREC, Bradenton, FL, during two-week intervals
beginning 1 December for the 36-year period from 1954 through
--- --- --
the season progresses (Figure 3). On 16 November, there is -a 91% probability that
there will be a freeze sometime during the winter. The freeze probability gradually
decreases to 62% by 16 January. Traditionally, this is the time when many growers
are thinking about or actually transplanting tomatoes, yet there is a chance of freezes
in about two out of three years on this date. By 1 February, the chance of a freeze
has decreased to 10 in 25
years, and by 15 February
the freeze probability has
decreased to 10 in 58 years.
There is essentially no freeze
probability 3% or 10 in
350 years by 1 March.
| I As previously indicated,
S freezes with devastating
I M consequences to Florida
RII 2 occurred frequently during
4 s M IONI.E di. S,1 3 V the 1980's (Table 1).
,. Freezes that were particularly
damaging to west central
Florida vegetable crops were
Figure 3. Probability of a freeze event occurring after the indicated those of 3, 4 March 1980, 21-
date at the GCREC, Bradenton, FL, during two-week 23 January 1985, and 25
intervals beginning 16 November for the 36-year period from F a
1954 through 1989. February and 4 December,
1989. Because of the spring
and fall cropping patterns for low-temperature sensitive vegetables in this area,
other freezes were less damaging.
Although the data and probabilities presented herein apply only to this specific
site, their use can be extended in a general way to the Manatee-Hillsborough County
vegetable production area. Generally, freeze probabilities will be somewhat greater
in areas north and east of the Gulf Coast Research and Education Center, whereas
lower freeze probabilities can be expected at locations west and south of the
Research Center. Therefore vegetable growers in west central Florida can use the
freeze probabilities presented in this report to schedule cropping cycles to coincide
with the periods of least likelihood of freezes. However, even with the best
planning, a freeze may occur outside of the probabilities listed herein. Other
publications provide information on prevention of freeze damage to crops by use of
sprinkler irrigation (3) and row covers (4).
Table 1. Occurrence of freezes at
Center during the 1980's.
Gulf Coast Research and Education
11ta err perau re
1. Barrick, W E. and R. J. Black. 1980. Florida climate data. Florida
Cooperative Extension Service Circular EES-5.
2. Bradley, J. T. 1975. Freeze probabilities in Florida. Florida Agricultural
Experiment Station Technical Bulletin 777.
3. Harrison, D. S., J. F. Gerber, and R. E. Choate. 1974. Sprinkler irrigation for
cold protection. Florida Cooperative Extension Technical Circular 348.
4. Hochmuth, G. J., S. Kostewicz, and W. Stall. 1987. Row covers for commercial
vegetable culture in Florida. Florida Cooperative Extension Service Circular 728.
5. Stanley, C. D. 1990. Temperature and rainfall report for 1989. Bradenton
GCREC Res. Rept. BRA1990-5.