WIXLIB

NOAA Technical Memorandum NWS WR-274Climate of Prescott, ArizonaBob Fogarty, Michael Staudenmaier Jr, 1st Revision by Michael Staudenmaier1January 20091National Weather Service Office, Flagstaff ArizonaUnited StatesDepartment of CommerceCarlos M. Gutierrez, SecretaryNational Oceanic andAtmospheric AdministrationVADM C. LautenbacherUnder SecretaryNational Weather ServicesDr. John (Jack) Hayes, Assistant Administratorfor Weather Services

And is approved for publication byScientific Services DivisionWestern RegionAndy Edman, ChiefScientific Services DivisionSalt Lake City, UT

CONTENTSI.PageClimate of Prescott, Arizona .1Climate Summary .5II.Temperature RecordsDaily Maximum and Minimum Temperature Extremes.7Highest and Lowest Average Temperatures by Month .19Warmest and Coldest Winter, Spring, Summer, and Fall.22Highest and Lowest Annual Temperatures.24Average Number of Days Per Year with Maximum Temperatures85, 90, and 95 Degrees or Higher .24Average Number of Days Per Year with Minimum Temperatures40, 32, and 10 Degrees or Lower.25Freeze and Growing Season Data .25Greatest Number of Consecutive Days with Maximum Temperatures90 degrees or Higher.26Greatest Number of Consecutive Days with Maximum Temperatures95 degrees or Higher.26Greatest Number of Consecutive Days with Maximum Temperatures100 degrees or Higher 27Greatest Number of Consecutive Days with Minimum Temperatures10 degrees or Lower.27III.Precipitation RecordsGreatest Daily 24-Hour Precipitation (7 A.M. to 7 A.M.).29Maximum and Minimum Precipitation by Months .32Wettest and Driest Seasons.34Yearly Precipitation Totals .3615 Wettest and Driest Precipitation Years .37Greatest Number of Days with 0.01 Inch and 0.10 Inchor More, with Average Number of Days .38Greatest Number of Days with 0.25 Inch and 0.50 Inchor More, with Average Number of Days .38Greatest Number of Consecutive Days with 0.01 Inchand 0.25 Inch or More.39Greatest Number of Consecutive Days with 0.50 Inchand 0.75 Inch or More.40Greatest Number of Consecutive Days without Measurable Precipitation .40Excessive Storms .41Greatest Daily 24-Hour Snowfall .42Maximum Monthly Snowfalls .45

First and Last Snowfalls .46Seasonal Snowfall Totals.4715 Snowiest and Least Snowy Seasons .48Greatest Number of Days with Snowfall of One Inch or More andThree Inches or More.49Greatest Number of Days with Snowfall of Six Inches or More.49Snowiest Calendar Days .50Snowiest Consecutive Two Calendar Days .50Excessive Snowstorms.51Number of Days with Snowfall of 1 Inch or More.51IV.Miscellaneous InformationNormal Heating and Cooling Degree Days .53Monsoon Statistics .54Normal Daily Maximum, Minimum, and Mean Temperatures.55Sunrise and Sunset Table .68

I. NARRATIVE GEOGRAPHICAL AND CLIMATOLOGICAL SUMMARY

Winter weather typically beginsby November and becomes wellentrenched by December, withincreasingly colder weather. ByDecember, minimum temperatures aregenerally in the low 20s; howeverafternoon maximum temperatures stillaverage in the 50s, due to the amount ofsunshine the station receives.CLIMATE OF PRESCOTT,ARIZONAPrescott is located at the foot ofthe northern end of the BradshawMountains in central Arizona at 5200feet elevation. To the south of the citythe mountains rise to peaks of 7900 feet;to the north the terrain slopes gentlydown the valley of Granite Creek to itsjunction with the Verde River.By mid-April, winter weatherusually begins to break, and warm spellsbecome more frequent. Spring inPrescott is typically breezy and dry withlittle precipitation occurring in May andearly June.Prescott s elevation of 5200 feetassures a variety of weather includingcool winters, warm summers, moderatehumidity, and considerable diurnaltemperature changes. Only limitedfarming is carried on because of therelatively short of the growing season.The average date of the last occurrenceof 32 F in the spring is May 16 and thatof the first 32 F temperature in the fall isOctober 10. The average precipitationfor Prescott is 19.19 inches.There are two distinct periods ofprecipitation in Prescott. One occursduring the winter months fromNovember through April when the jetstream is located over the state, allowingmoist Pacific storm systems to moveover the area. The other distinct periodis classified as the summer rainy season,or summer monsoon. The monsoonrainy period usually occurs during Julyand August when most of Arizona issubjected to widespread thunderstormactivity. These thunderstorms areextremely variable in intensity andlocation and occur mainly between thehours of 12 p.m. and 8 p.m.Summers in Prescott have anaverage maximum temperature (averagemaximum for June, July and August) of86.2 F (the all-time record high is105 F). On average, only 37 days in thesummer have maximum temperatures of90 F or higher. Summer minimumtemperatures are cool and refreshingwith low temperatures mainly in the 50s.Since there is no concentration ofindustry, smoke pollution is almostnonexistent, and the air is remarkablyfree of contaminants of any kind,although smoke from resident sfireplaces can accumulate on some of thecolder nights due to strong radiationalinversions that develop. Smoke fromprescribed burning, and more rarely aforest fire, can also be an occasionalissue during the spring, early summerand later in the fall.The moderate summer heat givesway to a cooler but nonetheless pleasantfall period with average maximumtemperatures generally ranging from80 F down to 50 F by the end of theseason and minimum temperaturesnormally falling below freezing by themiddle of October.1

A HISTORY OF WEATHEROBSERVATIONS AT PRESCOTTPlant on Sun Dog Ranch Road. This iswhere the observations are taken today.The first official weather stationin Prescott was established May 1, 1898.The office was located at 140 SouthMcCormick Street. The first observerwas Dr. Warren E. Day.In addition to this station there isan automated site at Love Field.Observations have been taken theresince July 2, 1948. On February 3, 1999the Automated Surface ObservingSystem (ASOS) was installed andcontinues to provide 24 hours per dayobservations.In May 1908, the station wasmoved to the Pamsetgaaf Sanitorium,which was one-half mile west southwestof the previous location. The wordPamsetgaaf is an acronym for Pure Air,Maximum Sunshine, EquableTemperature, Good Accommodation,and Food. The station was moved to aslightly lower elevation site in 1924, butremained on the sanitorium grounds.SOME HIGHLIGHTS OF THEWEATHER RECORDS INPRESCOTTMany unusual weather eventshave taken place in Prescott sinceofficial weather observations began onMay 1, 1898. The following is a briefdescription of some of the more extremeconditions recorded.On December 21, 1937, theweather station was moved to 617 EastWillis Street.During the 1940s the stationexperienced several moves. The firstoccurred on June 1, 1940 to 233 NorthVirginia. Then on July 5, 1944, thelocation was moved to the ArizonaHighway Department about one-halfmile southeast of the previous locationon North Virginia.The all-time record hightemperature for Prescott of 105 Foccurred on July 17, 1925. It occurredduring a short heat wave. Four days outof the six day period from the 13ththrough the 18th had high temperaturesof 100 F or greater, and on the 17thPrescott also set a record high lowtemperature of 70 F.On August 12, 1945, the weatherstation moved to the Prescott Fire Hallon Cortez Street where it stayed until1956. On February 24 of that year theobserving location moved to RadioStation KYCA one mile northeast of thePrescott post office.The all-time record warmestminimum temperature for Prescott wasfirst set on July 15, 2003 when themercury fell to only 76 F. It was thentied on July 6, 2007 when the sametemperature was recorded for theminimum temperature.On January 1, 1970, the weatherstation moved to 601 Flora Street. Itremained on Flora Street until 1983when it made one final move on April 25to the Sun Dog Wastewater TreatmentThe longest consecutive stretchof days with maximum temperatures of95 F or greater in Prescott was 17 days.This occurred during June 20 - July 6,1929. The highest temperature reached2

The most precipitation everrecorded in one calendar year at Prescottwas 39.47 inches, set during 1905. Theleast precipitation recorded in onecalendar year at Prescott was 3.41inches, set in 1907. The average annualprecipitation for Prescott is 19.19 inches.during this longest stretch of warmweather was 103 F.The longest consecutive stretchof days with maximum temperatures of90 F or greater in Prescott was 33 days.This occurred during June 18 - July 20,1905.The all-time record for heaviestprecipitation during any calendar day atPrescott was 4.28 inches which was seton November 27, 1919. This day was inthe middle of one the wettest periods ofPrescott’s weather history during which5.23 inches fell in a six day period. Theentire event ended with an accumulationof 13 inches of snow.The maximum number of days ina calendar year with temperatures of95 F or greater was 35 set in 1905. Themaximum number of days in a year withtemperatures of 90 F or greater was 81days which was set in 1933The coldest temperature everrecorded in Prescott was -21 F whichwas observed on January 22, 1937.Although the temperature warmed 47degrees that afternoon, the maximum of26 F was still the record low maximumfor the date.The most precipitation to occurwithin a continuous stormy periodoccurred from February 11-19, 1927when in excess of 10.59 inches fell. Theexact total is not known, because on the13th the record shows there were 5.0inches of snowfall and 0.00 inches ofprecipitation. It is possible that the actualtotal for the nine day period wasbetween 11 and 12 inches.The maximum number ofconsecutive days with minimumtemperatures of 10 F or lower was 12days. This has happened twice; firstfrom December 15-26, 1928 and againfrom December 28, 1932-January 8,1933.Because of this excessiveprecipitation event, February 1927 wasthe wettest month on record, with 10.59inches of precipitation falling during themonth.The maximum number of days ina calendar year with temperatures of10 F or lower was 32 days set in 1933.The maximum number of days in anymonth with temperatures of 10 F orlower was 23 days set in the extremelycold month of January 1937. Theaverage minimum temperature thatmonth was 3.8 F which was about 20degrees below normal. Of those 23 days,14 had low temperatures equal to orbelow 0 F and included the all timerecord low temperature.The average yearly snowfall inPrescott is 20.4", but is extremelyvariable from year to year. The mostsnowfall ever recorded during the snowseason (July - June) was 97.4 inches in1931-32. On the other extreme, severalseasons have recorded no snowfall, themost recent in 1913-14.3

total of 99 days! The greatest number ofconsecutive days with measurableprecipitation was 13 set during theperiod of July 6-18, 1953, when a totalof 5.42" of precipitation fell.The snowiest day in Prescott’sweather history was January 11, 1930when 21.8" fell. This was in the middleof the most snowfall to occur within acontinuous stormy period. From January10-13, 1930 there was 39.5" of snowmeasured.The greatest number ofconsecutive days with measurablesnowfall was 6 days set three times,most recently from February 11-16,1978. Interestingly, there were only 6.0"of snow during this period. The othertwo six day periods are on the list ofexcessive snow storms.January 1949 was the snowiestmonth with 53.0” recorded.The greatest number ofconsecutive days without measurableprecipitation was recorded fromSeptember 25, 1999 – January 1, 2000, a4

CLIMATE SUMMARYTEMPERATURE*RECORD NORMAL1 NORMAL1 NORMAL1 AL105-211 Climatological normals 1971-2000.* All values are 1.421.31.286.962.746.019.1939.471 Climatological normals 1971-2000.** All values are inches.520.497.4

II. TEMPERATURE RECORDS6