WE HAD A RARE COMBINATION OF AN UNSEASONABLY COOL APRIL AND UNSEASONABLY WARM MAY THIS SPRING IN PHILADELPHIA. SINCE 1872, THIS COMBINATION HAS OCCURRED ONLY THIRTEEN TIMES AND NOT SINCE 1982. BY DEFINTION UNSEASONABLY COOL/NORMAL/ UNSEASONABLY WARM MONTHS ARE DIVIDED INTO THIRDS. THE FOLLOWING ARE TEMPERATURES THAT OCCURRED IN PHILADELPHIA DURING THE ENSUING SUMMERS. ONLY NINE OF THE THIRTEEN YEARS ARE LISTED BELOW BECAUSE THE FOUR OTHER SUMMERS TRENDED TOWARD OR WERE ALREADY IN EL NINO. CURRENT EXPECTATIONS ARE FOR THE MAIN ENSO REGION KNOWN AS NINO3.4 IN THE EASTERN EASTERN PACIFIC TO HAVE LA NINA CONDITIONS DEVELOP THIS UPCOMING SUMMER.
YEAR JUNE AVG JULY AVG AUGUST AVG SUMMER AVG SUMMER PCPN 1887 71.6 80.6 74.0 75.4 16.26 1904 70.8 74.8 73.4 73.0 11.13 1914 72.0 74.0 76.2 74.1 13.76 1936 71.8 77.3 76.0 75.0 9.86 1937 72.6 77.1 77.2 75.6 8.77 1939 73.2 76.2 77.8 75.7 13.54 1944 72.2 78.4 75.4 75.3 7.06 1964 72.4 76.6 72.2 73.7 4.53 1975 72.2 76.6 77.1 75.3 16.10 AVG 72.1 76.8 75.4 74.8 11.22 1971-2000 NML 72.3 77.6 76.3 75.4 11.50ON A SEPARATE NOTE A CONDITIONAL TEMPERATURE FORECAST FOR PHILADELPHIA INTERNATIONAL AIRPORT BASED ON THE ENSO STATE, WHEN THE FIRST HEAT WAVE OF THE SEASON OCCURS AND THE MEAN APRIL MINMIMUM TEMPERATURE CAN BE FOUND AT OUR WEB SITE AT: WWW.ERH.NOAA.GOV/PHI/REPORTS/ONIHEATWEB2007V1.PDF. ITS ALL LOWER CASED LETTERS EXCEPT FOR THE LETTERS ONIH IN ONIHEATWEB...
THE OFFICIAL CPC OUTLOOK FOR THE SUMMER IS FOR A GREATER CHANCE OF IT BEING WARMER THAN COOLER THAN NORMAL.