April 2018 Temperature and Precipitation Summary Arizona Climate Summary May 2018 Summary of conditions for April 2018 April 1 st 16 th : April was a very dry month across Arizona. Several low pressure systems passed north of Arizona during the first week of April, but no precipitation was reported in the state. Temperatures were roughly 10 degrees above normal statewide. Three more low pressure systems crossed Utah and Colorado in the second week of April, and again the precipitation bypassed Arizona. Phoenix had its first 100 o F day of the year on the 10 th. While the precipitation missed the state, the winds from the storms did not. April was quite windy across Arizona, particularly northern Arizona, and when combined with the hot and dry weather, fire danger is extreme across most of the state. Several wildfires are still burning and fire danger will remain very high until the monsoon rainfall begins. The dry conditions also exacerbated the drought, and led to the expansion of Extreme Drought (D3) through Yuma County and the introduction of Exceptional Drought (D4) in Apache and Navajo counties (see P.10). The Navajo Nation declared a drought emergency in April. April 17 th 30 th : By the 17 th another strong low pressure system moved south from the Pacific Northwest into Nevada and Utah, bringing rain and snow to those states, but Arizona only benefitted by some cooler temperatures. On the 19 th, yet another system moved south through California and finally on the 20 th, rain was reported across northern Arizona. Flagstaff had 0.06, Grand Canyon AP had 0.08, Page had 0.09, St. Johns had 0.05, Window Rock had 0.02, Winslow had 0.08, and Bellemont had 0.20. On the 21 st, St. Johns had another 0.11, Window Rock had 0.02, and Bellemont had 0.19, Petrified Forest had 0.14, and Show Low had 0.08. During this storm temperatures only dipped slightly on the 20 th as it was a warm storm. High pressure returned and temperatures quickly rebounded to 10 degrees or more above normal. The southwest deserts had temperatures in the upper 90s while the higher elevations reached the lower 70s. Nighttime temperatures were in the lower 60s in the deserts and in the mid 20s at the higher elevations. On the 25 th Castle Hot Springs reached 100 o F, and on the 27 th Eloy and Phoenix reached 100 o F. This was the second day of 100 o F for Phoenix. From the 28 th through the 30 th another system moved across the state with very high winds but the storm stalled no further precipitation fell in the state during April. In This Issue: Overview of April, graphs of the April daily maximum and minimum temperatures, precipitation, mean daily dew points for Flagstaff, Phoenix, and Tucson; April climate statistics, maps of mean monthly maximum and minimum temperatures, precipitation, dew points, wind speeds for April; short-term drought maps for the beginning and end of April 2018; Long-term Drought Map through April; and graphs of the mean April temperature and precipitation for the period of record for Tucson, Phoenix, and Flagstaff, graphs of the cumulative precipitation for the calendar year for Flagstaff, Phoenix, and Tucson. Climate calendars for Flagstaff, Phoenix, Tucson, Prescott, Winslow and Yuma, including daily and monthly normals and extremes, for each month of the year, are not yet updated through 2017. See p.21 of this report for calendar abbreviations. Data are preliminary and are from the National Weather Service Forecast Offices in Flagstaff, Phoenix and Tucson. **Note: The discrepancy between the Statewide Temperature and Precipitation values for Phoenix, Flagstaff and Tucson and the daily values in their graphs are due to the reporting times. Statewide Temperature and Precipitation values are taken at 5pm, while official daily records at the airports are taken from Midnight to Midnight. Dr. Nancy J. Selover, State Climatologist http://azclimate.asu.edu 480-965-0580 Edited by Nancy J. Selover 2018 Arizona State Climate Office 1
April 2018 Daily Temperature, Precipitation, & Dew Point for Flagstaff, Phoenix, and Tucson 2
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FLAGSTAFF CLIMATE STATISTICS April 2018 This April was the 6 th warmest on record and tied for 4 th driest with 1916. Avg Max Temp(F) 64.4 Normal 58.2 Avg Min Temp(F) 31.3 Normal 28.5 Avg Mean Temp(F) 47.8 Normal 43.3 Departure from Normal (F) +4.5 Highest Monthly Avg Temp (F) 50.4 in 1989 Lowest Monthly Avg Temp (F) 36.2 in 1975 Highest Temp this month (F): 75 on 26 th Lowest Temp this month (F): 21 on 19 th Record High (F): 80 on 4/7/1989, 4/28/1992 Record Low (F): -2 on 4/02/1975 Temperature or precipitation records this month: 8 th HiMin 44 set, previous record 41 in 2007 Flagstaff Number of Days of: Minimum Temp 35 o F or higher 10 Minimum Temp 30 o F or lower 14 Maximum Temp 70 o F or higher 9 Maximum Temp 60 o F or lower 8 Heating Degree Days 509 Normal 649 Cooling Degree Days 0 Normal 0 Degree base 65 o F Total April Precipitation 0.06 Normal April Precipitation 1.15 Departure from normal -1.09 Greatest 24-Hr Precipitation 0.06 on 20 th Total Precipitation Year-to-Date 5.01 Departure from Normal -2.41 Total April Snowfall Trace Normal 7.1 Record April Snowfall 58.3 in 1965 Number of Days: Clear 28 Partly Cloudy 2 Cloudy 0 Greatest April Precipitation 5.62 in 1965 Least April Precipitation: 0.00 in 1991 Average Wind Speed Highest Peak Gust 9.8 mph 57 mph from 200 o on 19 th PHOENIX CLIMATE STATISTICS April 2018 This April was the 3rd warmest on record and tied for the driest April with 31 other years. Phoenix still has had only 6 days of rain since January 1 st and only 8 days of rain since Aug 23 rd. Avg Max Temp(F) 90.6 Normal 85.2 Avg Min Temp(F) 64.3 Normal 60.2 Avg Mean Temp (F) 77.4 Normal 72.7 Departure from Normal (F) +4.7 Highest Monthly Avg Temp (F) 80.0 in 1989 Lowest Monthly Avg Temp (F) 62.4 in 1967 Highest Temp this month (F) 100 on 10 th, 27th Lowest Temp this month (F): 54 on 18 th Record High (F): 105 on 4/22/2012, 4/29/1992, 4/20/1989 Record Low (F): 35 on 4/10/1922 4 Temperature or precipitation records this month: 6 th HiMin 67 tied, first set in 2002 7 th HiMin 69 tied, first set in 1989 8 th HiMin 74 set, previous record 70 in 1989 10 th HiMax 100 tied, first set in 1989 Phoenix Number of Days of: Minimum Temp 60 o F or lower 8 Minimum Temp 70 o F or higher 4 Maximum Temp 80 o F or lower 3 Maximum Temp 95 o F or higher 9 Heating Degree Days 0 Normal 17 Cooling Degree Days 381 Normal 251 Degree base 65 o F Total April Precipitation 0.00 Normal April Precipitation 0.28
Departure from normal -0.28 Greatest 24-Hr Precipitation 0.00 Total Precipitation Year-to-Date 0.77 Departure from Normal -2.33 Greatest April Precipitation 3.36 in 1926 Least April Precipitation 0.00 in 2008, 2000 and 30 other years Number of Days: Clear 8 Partly Cloudy 20 Cloudy 2 Average Wind Speed 7.6 mph Highest Peak Gust 44 mph from 270 o on 12 th TUCSON CLIMATE STATISTICS April 2018 This April was the 2nd warmest on record and was tied with 26 other years for the driest April on record. Avg Max Temp(F) 88.4 Normal 82.1 Avg Min Temp(F) 56.8 Normal 52.0 Avg Mean Temp(F) 72.6 Normal 67.0 Departure from Normal (F) +5.6 Highest Monthly Avg Temp (F) 73.8 in 1989 Lowest Monthly Avg Temp (F) 57.8 in 1975 Highest Temp this month (F): Lowest Temp this month (F): 96 on 10 th, 27 th 43 on 14 th Record High (F): 104 on 4/20/1989, 4/21/1989 Record Low (F): 27 on 4/04/1945 Temperature or precipitation records this month: 10 th HiMax 96 tied, set in 1907 and 1989 11 th HiMax 95 tied, set in 1907 and 1988 Tucson Number of Days of: Minimum Temp 50 o F or lower 5 Minimum Temp 60 o F or higher 12 Maximum Temp 80 o F or lower 4 Maximum Temp 95 o F or higher 7 Heating Degree Days 12 Normal 60 Cooling Degree Days 247 Normal 121 Degree base 65 o F Total April Precipitation 0.00 Normal April Precipitation 0.31 Departure from normal -0.31 Greatest 24-Hr Precipitation 0.00 Total Precipitation Year-to-Date 1.98 Departure from Normal -0.86 Greatest April Precipitation 3.53 in 1905 Least April Precipitation 0.00 in 1895, 1950, 2002, and 23 other years. Number of Days: Clear 28 Partly Cloudy 0 Cloudy 0 Average Wind Speed Highest Peak Gust 7.9 mph 42 mph from 210 o on 12 th Data are from the National Weather Service and the National Climatic Data Center and are preliminary. 5
Wind Speeds for April: Day Phoenix Flagstaff Tucson (mph) Avg Max Avg Max Avg Max 1 7.1 24 7.4 29 6.4 24 2 9.4 23 10.9 43 11.1 32 3 4.8 18 4 22 6.6 21 4 5.5 20 6.6 32 6.3 22 5 6.4 21 5.5 31 7.2 22 6 7.4 26 11.1 39 7.4 34 7 6.8 24 12 41 6.4 27 8 9.1 24 11.5 37 8.1 30 9 4.2 10 7.1 29 5.3 18 10 4 17 4.2 24 6.6 23 11 6.9 26 13.8 43 7.3 27 12 16.4 44 19.3 56 14.3 42 13 15.2 40 9.4 32 11.4 36 14 8.1 22 9 40 5.4 22 15 6.4 21 8.1 31 5.6 18 16 6.7 23 20.5 50 13 33 17 10.1 27 13.6 54 10.3 28 18 6 17 8.2 25 5.5 20 19 11 19 16.1 57 13.5 40 20 9 27 8.3 29 7.4 25 21 5.2 20 4.5 21 5.9 17 22 5.4 21 4 26 5 17 23 5.6 18 7 33 5.7 19 24 6.1 21 6.9 29 6.2 28 25 4.7 17 7.1 23 4.9 18 26 5.8 23 4.6 30 5.7 20 27 6.7 21 5.9 32 6.5 27 28 9 36 11.8 43 8.2 31 29 9.8 28 20.4 48 12.5 36 30 8.7 26 16.6 37 9.9 36 Dew Points for April: Daily Average Dew Point ( o F): Day Phx Tuc Flg 1 16 13 15 2 24 17 19 3 29 21 20 4 32 24 23 5 32 26 25 6 34 29 31 7 42 35 27 8 28 28 21 9 20 19 10 10 22 15 15 11 21 22 16 12 6 4 6 13 7 6 4 14 9 4 6 15 15 5 6 16 16 12 7 17 13 8 1 18 18 10 7 19 25 20 21 20 30 21 20 21 32 23 21 22 29 26 19 23 27 23 18 24 27 21 18 25 29 24 19 26 33 29 21 27 34 32 25 28 27 25 14 29 27 24 20 30 24 23 13 6
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April 2018 The minimum temperatures ranged from 10 o F at Grand Canyon National Park and Sunset Crater to 59 o F at Litchfield Park. The lowest maximum temperature of 62 o F was recorded at Snowslide Canyon and the highest was 107 o F at Havasu. The highest rainfall totals were 0.70 at Maverick Fork and Wildcat and the lowest was 0.00 at many stations. The lowest average dew point was 11 o F at Window Rock and the highest was 40 o F at Parker. The highest peak wind gust, other than Flagstaff, Phoenix and Tucson was 41 mph at Bonita. Average wind speeds ranged from 2 mph in the Phoenix area to 14 mph at Show Low Airport. 8
T April 2018 The highest average minimum temperature was 66 o F at Falcon Field, and the lowest average minimum temperature was 24 o F at Grand Canyon National Park. The highest average maximum temperature was 94 o F at Yuma, Havasu, Bullhead City and Bartlett Dam and the lowest average maximum temperature was 53 o F at Snowslide Canyon. 9
Short term drought maps for March 27 th on left and May 1 st on right. The extremely dry April led to an expansion of Severe Drought (D2) through northern Mohave County. Extreme Drought (D3) expanded through western Pinal and southern Maricopa to the California border through Yuma County. Arizona and expanded across the northeast counties. Exceptional Drought (D4) was introduced into Apache and Navajo counties and covers 9.62% of the state. Extreme Drought (D3) increased from 46.5% of the state last month to 50.7% by the end of April. Drought impacts include native vegetation dying in some areas of the state, water hauling for livestock and wildlife, decimated forage, supplementing feed for livestock, culling herds and dry soils leading to increased blowing dust. 10
Long-term drought map for April for Arizona shows hydrologic drought, and this month it is based on precipitation and evaporation using the Standardized Precipitation Evaporative Index (SPEI) over the past 24-, 36-, and 48-months. While a few areas are shown as No Drought, these are mostly likely due to a lack of data, as the entire state is experiencing a long-term deficit of precipitation and reduced recharge to aquifers and reservoirs, as well as enhanced evaporation due to the high temperatures. 11
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April April minimum temperatures were 2 to 6 o F warmer than average across the state with slightly cooler than average temperatures at the border of Gila, Coconino and Yavapai counties. Daytime temperatures were 2 to 8 o F warmer than average across the state. April was much drier than March with virtually the entire state receiving less than 25% of normal precipitation. The lack of winter storms caused both the dry conditions and the warmer than normal temperatures in the state. 13
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Calendar Year 2018 Calendar year minimum temperatures across Arizona were generally within 2 o F of average with warmer conditions in the southwest and much warmer than normal conditions in La Paz County, and cooler than normal conditions in the northeast. Daytime temperatures have been 0 to 6 o F warmer than average statewide. Since January, most of the state has received less than 70% of average precipitation though the southwest third of the state has received less than 50% of average. Southeastern Arizona and southern Apache County received over 100% of average precipitation, primarily from February storms. 15
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s aham, Cochise, La Paz, OPima and 2018 Water Year Water Year 2018 minimum temperatures have ranged from 2 o F cooler than normal to 4 o F warmer than normal across the state. Daytime temperatures have been 2 to 6 o F warmer than normal statewide, with a few pockets that have been 6 to 8 o F warmer than average. The entire state has received less than 50% of normal precipitation since October 1 st in one of our driest winters on record. The southwest, central Arizona, and central Navajo County have received less than 25% of normal precipitation. The run-off into the reservoirs and streams is forecast to be near record low values this year, and the upper Colorado snowpack is also extremely low. 17
April Mean Temperature Graphs Flagstaff, Phoenix, and Tucson 1895-2018: 18
April Mean Precipitation Graphs Flagstaff, Phoenix, and Tucson 1895-2018 19
2018 Cumulative Precipitation Graphs Flagstaff, Phoenix and Tucson: Flagstaff is 2.41 below normal, Phoenix is 2.33 below normal, and Tucson is 0.86 below normal. 20
The downloadable normals and extremes calendars use the following abbreviations: NORM = 30 year (1971-2000) average value (degrees Fahrenheit (F)) OBS = The temperature observation for that day this year AVG = Average daily temperature HI MAX = Highest maximum temperature for that day (F) LO MAX = Lowest maximum temperature for that day (F) LO MIN = Lowest minimum temperature for that day (F) HI MIN = Highest minimum temperature for that day (F) Mx PCP = Maximum precipitation for that day (inches) Mx SNO = Maximum snowfall for that day (inches) 21