FINAL Fall 2012 Frost/Freeze Recap

Fall 2012 Frost/Freeze Recap: Considering that "first fall-freeze dates" across the NWS Hastings coverage area in South Central Nebraska and North Central Kansas can sometimes vary by 5 weeks or more from one year to another, it can be difficult to put one particular season into perspective. However, when taking into account 30-year averages of the first occurrence of 32 and 28 degrees (or colder), the majority of the NWS Hastings coverage area met these temperature thresholds at least slightly earlier than average during Fall 2012...in some cases two to three weeks earlier. Many places recorded their earliest hard freeze (temperatures of 28° or colder) since at least 2000. Despite this somewhat early onset of freezing temperatures this fall, the 2012 growing season was nonetheless among the longest on record in most places thanks to an incredibly early last spring freeze. Compared to Fall 2011, most places recorded their first fall freeze roughly two weeks later this year. 

As is typically the case, northern portions of the Nebraska coverage area notched the first sub-freezing temperatures of the fall, including readings of 30° at Greeley and York on the morning of Sep. 23rd. About a week later, more places in southern Nebraska nudged below freezing on Oct. 2, including Kearney airport (31°), Cambridge (31°) and Holdrege (29°). Focusing specifically on a hard freeze, Oct. 2 brought the first of these readings with 28° at Greeley. However, for the vast majority of South Central Nebraska and North Central Kansas, the first legitimate, widespread hard freeze and frost of the season arrived on the mornings of Oct. 6th or 7th, with the ENTIRE area plunging well into the 15-28° range on the morning of the 7th.

Please refer to the table located farther down the page for a wealth of information on average frost/freeze dates along with Fall 2011 results for 13 chosen locations across the NWS Hastings coverage area. Based on the results in the table, here are just a few "highlights" involving locations that strayed at least 10 days from average frost/freeze dates:

First occurrence of 28° (hard freeze) or lower:
 
Kearney airport (Oct. 6) was 10 days earlier than average, and the earliest since 2000
York 3N (Oct. 7) was 14 days earlier than average, and the earliest since 2009
Holdrege (Oct. 5) was 16 days earlier than average, and the earliest since 1995
Hastings airport and NWS Office (Oct. 6) was 13 days earlier than average, and the earliest since 2000
Hebron (Oct. 7) was 13 days earlier than average, and the earliest since 2000
Smith Center KS (Oct. 7) was 13 days earlier than average, and the earliest since 2000
Plainville KS 4 WNW (Oct. 7) was 20 days earlier than average, and the earliest since 2000
Beloit KS (Oct. 7) was 19 days earlier than average, and the earliest since 2000

First occurrence of 32° (freezing) or lower: 
York 3N (Sep. 23) was 19 days earlier than average, and the earliest since 1995
Plainville KS 4 WNW (Oct. 6) was 11 days earlier than average, and the earliest since 2004
Beloit KS (Oct. 7) was 10 days earlier than average, and the earliest 2001


 
Before continuing, here are a few definitions:

- Frost occurs when there is a solid deposition of water vapor from the air. Frost will form when solid surfaces are cooled below the dew point. An air temperature range of 33-36° along with very light winds is usually needed to initiate frost formation. Minor damage is possible to some plants. One must keep in mind that a frost is not guaranteed at these temperatures if moisture in the air is lacking. The range of average dates for the first occurrence of fall frost across most of south central Nebraska and north central Kansas is between Sep. 23 - Oct. 5.

- Freeze occurs when the air temperature drops to 32° or lower. A freeze will result in significant damage to many unprotected plants, especially if the temperature remains at the freezing mark for a few hours. The range of average dates for the first freeze of the fall across most of south central Nebraska and north central Kansas is between
Sep. 27 - Oct. 17.


- Hard Freeze occurs when the temperature reaches 28° or lower for at least a few hours. It usually means that many types of plants and most seasonal vegetation will be destroyed. The range of average dates for the first hard freeze of the fall across most of south central Nebraska and north central Kansas is between Oct. 6 - Oct. 27.



Detailed Fall Frost/Freeze Table and Climatological Maps:

Below is a table and set of maps, primarily focused on average dates for reaching particular temperature frost/freeze thresholds. However, there is often tremendous variation from year-to-year and between any given location across the area (see bottom of page for details on unusually early freeze in September 1974).

Examining the table below, here are a few things to consider:

- The first column lists 9 chosen locations in south central Nebraska and 4 in north central Kansas with long histories of being NWS Cooperative Observer sites (except for Grand Island and Hastings airports, which are automated systems). This is just a small sampling of dozens of observing locations within the NWS Hastings coverage area, and these sites are generally organized from north to south down the column.

- The second column shows the average date of the earliest observance of 36, 32, and 28 degree temperatures during the 30-year period from 1981-2010. Please note that differences in average freeze dates between these locations are NOT purely a function of "north versus south", but also depend on a variety of factors including local terrain. For example, Alton, KS, in Osborne County is typically prone to earlier freezes in the fall than some locations farther north, thanks to efficient cold air drainage along the South Fork Solomon River valley.

- The third and fourth columns reveal the earliest first freeze date and latest first freeze date (32 degrees or colder) observed during the past 32 years, covering the period 1981-2012. It is readily apparent that the phrase "average freeze date" is quite relative, as most sites have a 5-7 week difference between the earliest and latest dates. For the majority of locations, the earliest last freeze during the past 31 years occurred between Sep. 15th-22nd in years such as 1991 and 1993. On the opposite spectrum, for many locations the latest freeze during the past 31 years occurred between Oct. 23th- Nov. 4th in years such as 1997 and 1998.

- The final column on the right reveals the date that 36, 32 and 28-degree thresholds were first met THIS FALL within the area. A blue-shaded date indicates a location that reached a temperature threshold more than 7 days before the average date, while red-shaded dates indicates that this threshold was met more than 7 days after the average date.

 Climatological Data For South Central Nebraska and North Central Kansas
(All Averages Based on 30-year observations from 1981-2010)

 

Average First 
Date of...

36 Degrees
32 Degrees
28 Degrees

Earliest Date 
1981-2012 of...

32 Degrees
or Colder 

Latest Date 
1981-2012 of...

32 Degrees
or Colder 

First Fall 2012  
Occurence of...

36 Degrees
32 Degrees
28 Degrees

 Greeley

Sep. 23
Sep. 27
Oct. 6

Sep. 15,1993 

Oct. 14,1997

Sep. 18 (35°)
Sep. 23 (30°)
Oct. 2 (28
°)

 Osceola

Sep. 30
Oct. 9
Oct. 14

Sep. 19, 1991

Nov. 3, 1998

Sep. 23 (36°)
Oct. 5 (31°)
Oct. 6 (27°)

 Kearney Airport
(NWS Observer)

Sep. 27
Oct. 5
Oct. 16

Sep. 17, 1981

Oct. 25, 1997 

Sep. 23 (36°)
Oct. 2 (31
°)
Oct. 6 (28°)

 Grand Island
 (airport)

Sep. 29
Oct. 8
Oct. 15

 Sep. 19, 1991

 Oct. 26, 2007

Sep. 23 (34°)
Oct. 5 (32°)
Oct. 6 (25°)

 York 
(3 miles N)

Oct. 3
Oct. 12
Oct. 21

 Sep. 19, 1991

Nov. 4, 1998

Sep. 18 (35°)
Sep. 23 (30°)

Oct. 7 (21°)

 Cambridge

Sep. 25
Oct. 2
Oct. 12

Sep. 15, 2008

 Oct. 25, 1997

Sep. 18 (33°)
Oct. 2 (31°)

Oct. 7 (23°)

 Holdrege

Oct. 3
Oct. 10
Oct. 21

Sep. 19, 1991

Nov. 4, 1998

Sep. 18 (36°)
Oct. 2 (29°)

Oct. 5 (28°)

 Hastings
(NWS Office/airport)

Sep. 29
Oct. 9
Oct. 19

Sep. 19, 1991

 Nov. 3, 1998

Oct. 2 (34°) / Sep. 23 (35°)
Oct. 5 (30°) / Oct 5 (31°)
Oct. 6 (27°) / Oct 6 (27°)

 Hebron

Oct. 1
Oct. 11
Oct. 20

 Sep. 19, 1991

 Oct. 26, 1997
 Oct. 26, 2007

Sep. 23 (35°)
Oct. 7 (24°)
Oct. 7 (24°)

 Smith Center KS

Oct. 3
Oct. 13
Oct. 20

 Sep. 21, 1983

 Nov. 4, 1998

Oct. 5 (36°)
Oct. 7 (24°)
Oct. 7 (24°)

 Alton KS
(2 miles SW)

Sep. 26
Oct. 3
Oct. 13

 Sep. 15, 1993

 Oct. 23, 2007

Oct. 2 (33°)
Oct. 7 (21°)
Oct. 7 (21°)

 Plainville KS
(4 miles WNW)

Oct. 7
Oct. 17
Oct. 27

Sep. 20, 1995

 Nov. 4, 1998

Oct. 5 (34°)
Oct. 6 (32°)
Oct. 7 (27°)

 Beloit KS

Oct. 5
Oct. 17
Oct. 26

 Sep. 22, 1995

 Nov. 10, 1998

Oct. 7 (27°)
Oct. 7 (27°)
Oct. 7 (27°)



Median Dates of First Fall Freeze and Hard Freeze (1981-2010)
(Midwestern Regional Climate Center)

(click images to enlarge)

Median Date of First 32-Degree Freeze Median Date of First 28-Degree Hard Freeze

 


 

South Central Nebraska and North Central Kansas 
Average First Frost/Freeze Dates (1981-2011)

(click images to enlarge)

Average 36-Degree Date (First Possible Frost)
Average 32-Degree Date (First Freeze)
Average 28-Degree Date (First Hard Freeze)



Nebraska First Fall Frost/Freeze Averages (maps courtesy NWS Omaha/Valley)
(click images to enlarge)

Average date of first 36-degree temps

Average date of first 32-degree temps

Average date of first 28-degree temps

 



 Average First Fall 32-Degree Dates for Kansas (courtesy the Kansas State Climatologist)

(click to enlarge)



A Look Back At The Unusually Early Frost/Freeze of September 1974:

One of the earliest freezes on record in parts of South Central Nebraska occurred the first week of September in 1974, as many locations dropped below the freezing mark on September 3rd. A surface weather map (see below, far left thumbnail image) from September 3, 1974 depicted just why such cold temperatures were observed. An unseasonably cold airmass roared into the region behind a strong cold front. Eventually, surface high pressure set up over the region, creating an ideal situation for a record early freeze. In fact, note the hand written comment "Record early damaging frosts, corn belt area" at the top of the weather map. Cooperative Observation forms for Gothenburg and Greeley, Nebraska are also shown below. The Gothenburg observer noted "Clear. Froze. Ice. Crop Damage" on the right side of the form on the 3rd. Finally, it is interesting to note both Gothenburg and Greeley recorded freezing temperatures again just ten days later on September 13, 1974.  

September 3, 1974 Weather Map

(click to enlarge)

Gothenburg, NE Observation Form
September 1974

(click to enlarge)

Greeley, NE Observation Form
September 1974

(click to enlarge)

 

This page was composed by the staff at the National Weather Service in Hastings, Nebraska.

 



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