849
CXUS55 KBOI 011735
CLMBOI
CLIMATE REPORT
NATIONAL WEATHER SERVICE BOISE ID
1135 AM MDT MON JUN 01 2020
..THE BOISE ID CLIMATE SUMMARY FOR THE MONTH OF MAY 2020
TEMPERATURES AVERAGED JUST OVER ONE DEGREE ABOVE NORMAL.
PRECIPITATION WAS 40 PERCENT ABOVE NORMAL.
AN EXTENSIVE UPPER-LEVEL LOW PRESSURE SYSTEM OVER THE NORTHEAST
PACIFIC WAS THE DOMINANT FEATURE THROUGH THE 17TH. IT WAS
RESPONSIBLE FOR STEERING WEATHER SYSTEMS INTO WESTERN NORTH AMERICA.
BETWEEN SYSTEMS, SOUTHWEST FLOW EAST OF THE LOW BROUGHT WARMER AIR.
THE FIRST COUPLE OF WEATHER SYSTEMS, WHICH CAME THROUGH ON THE 3RD
AND THE 6TH, BROUGHT ONLY LIGHT PRECIPITATION. STRONG WEST WINDS
FOLLOWED A COLD FRONT ON THE MORNING OF THE 6TH. A GUST OF 48 MPH
WAS MEASURED AT THE AIRPORT.
THE FIRST SIGNIFICANT PRECIPITATION OF THE MONTH CAME ON THE 14TH
WHEN .36 INCH OF RAIN FELL AT THE AIRPORT AS A LOW PRESSURE TROUGH
CROSSED THE AREA.
ON THE 16TH A MUCH LARGER AND COLDER TROUGH FROM SIBERIA WAS NEARING
THE WEST COAST. BEFORE MOVING INLAND ON THE 19TH, IT HAD DEEPENED
FAR ENOUGH DOWN THE COAST TO TAP SUBTROPICAL MOISTURE SOUTHWEST OF
CALIFORNIA. ON THE 20TH IT WAS CENTERED DIRECTLY OVER IDAHO. THAT
DAY.80 INCH OF RAIN FELL AT THE AIRPORT, BREAKING THE PREVIOUS
RECORD FOR THE DATE OF.56 INCH IN 1985. OTHER PARTS OF TOWN WERE
DRENCHED BY EVEN HEAVIER RAIN, INCLUDING 1.31 INCHES AT BSU.
WITH A HIGH OF ONLY 51, THE 20TH WAS THE COOLEST DAY OF THE MONTH.
THE RECORD COOLEST HIGH TEMPERATURE FOR THE DATE IS 48 IN 1902.
BELOW-NORMAL TEMPERATURES WOULD CONTINUE THROUGH THE 24TH.
AN UPPER-LEVEL HIGH PRESSURE RIDGE BUILDING OVER THE COAST ON THE
24TH STARTED A WARMING TREND WHICH WAS BRIEFLY INTERRUPTED BY A
WEAK PACIFIC COLD FRONT ON THE 26TH.
STARTING ON THE 27TH, TEMPERATURES ROSE EACH DAY AS THE RIDGE
STRENGTHENED. FROM THE 28TH THROUGH THE 30TH, HIGHS WERE IN THE 90S
FOR THE FIRST TIME SINCE SEPTEMBER. ON THE 30TH THE HIGH OF 98 TIED
THE RECORD FOR THE DATE SET IN 1986. AND THE LOW OF 69 BROKE THE
PREVIOUS RECORD OF 65 SET IN 2015.
A LOW PRESSURE SYSTEM THAT HAD BEEN SPINNING OVER THE SUBTROPICAL
PACIFIC WEST OF BAJA FINALLY MOVED INLAND OVER CALIFORNIA ON THE
30TH. AS IT PROGRESSED NORTHWARD TOWARD EASTERN OREGON AND SOUTHWEST
IDAHO, IT WAS PRECEDED BY HOT DRY WINDY WEATHER AND SCATTERED
THUNDERSTORMS. PRECIPITATION WAS MOSTLY LIGHT. ONLY A TRACE OF RAIN
DAMPENED THE AIRPORT, BUT A FEW SPOTS CLOSER TO THE FOOTHILLS GOT
HEAVY DOWNPOURS.
THE PEAK GUST AT THE AIRPORT WAS 48 MPH FROM THE EAST-SOUTHEAST AT
5:43 PM MDT. WINDS WERE LIKELY STRONGER ELSEWHERE AROUND THE VALLEY,
AS THERE WERE REPORTS OF TREES DAMAGED OR BLOWN OVER AND POWER
OUTAGES.
BY THAT EVENING THE FIRST ROUND OF SHOWERS HAD MOVED NORTH AND EAST
OF BOISE, AND AT 9:15 PM MDT A COLD FRONT PASSED THE AIRPORT FROM
THE WEST.
THERE WAS MORE WEATHER TO COME LATER THAT NIGHT, AS THE UPPER-LEVEL
TROUGH BEHIND THE COLD FRONT WAS STILL ON ITS WAY. THE ARRIVAL OF
THE TROUGH WAS ANNOUNCED BY A THUNDERSTORM JUST BEFORE 3 AM MDT ON
THE 31ST. HAIL ONE-HALF INCH IN DIAMETER FELL AT THE AIRPORT, BUT
THERE WAS ONLY .09 INCH OF TOTAL PRECIPITATION.
THUNDERSTORMS BETWEEN MIDNIGHT AND 6:00 AM ARE VERY RARE IN OUR PART
OF THE COUNTRY. AT BOISE THE CHANCE IS ONLY 2 PERCENT IN MAY AND 4
PERCENT IN JUNE.
...............................
CLIMATE NORMAL PERIOD 1981 TO 2010
CLIMATE RECORD PERIOD 1875 TO 2020
WEATHER OBSERVED NORMAL DEPART LAST YEAR'S
VALUE DATE(S) VALUE FROM VALUE
NORMAL
..........................................................
TEMPERATURE (F)
HIGHEST 98 05/30
LOWEST 34 05/07
AVG. MAXIMUM 72.6 71.6 1.0
AVG. MINIMUM 48.4 46.5 1.9
MEAN 60.5 59.1 1.4
DAYS MAX >= 90 3
DAYS MAX <= 32 0
DAYS MIN <= 32 0
DAYS MIN <= 0 0
PRECIPITATION (INCHES)
RECORD
MAXIMUM 4.90 1890
TOTALS 1.98 1.39 0.59
DAYS >= .01 15
DAYS >= .10 4
DAYS >= .50 1
DAYS >= 1.00 0
GREATEST
24 HR. TOTAL 1.02 05/19 TO 05/20
SNOWFALL (INCHES)
TOTALS 0.0
SINCE 7/1 15.3
GREATEST
SNOW DEPTH 0
24 HR TOTAL 0
DEGREE DAYS
HEATING TOTAL 192 226 -34 173
SINCE 7/1 5102 5449 -347
COOLING TOTAL 58 41 17 22
SINCE 1/1 64 44 20
..........................................................
WIND (MPH)
AVERAGE WIND SPEED 7.8
HIGHEST WIND SPEED/DIRECTION 35/290 DATE 05/06
35/120 05/30
HIGHEST GUST SPEED/DIRECTION 48/280 DATE 05/06
48/110 05/30
AVERAGE RH (PERCENT) 51
- INDICATES NEGATIVE NUMBERS.
R INDICATES RECORD WAS SET OR TIED.
MM INDICATES DATA IS MISSING.
T INDICATES TRACE AMOUNT.
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