After experiencing near record-warmth in May (second warmest) and August (third warmest), 2015 can now lay claim to the warmest September on record, easily topping 1961's previous record by 0.9 degrees. Like much of the summer, September's average temperature was greatly influenced by the lack of any incursions of chilly air masses. The coolest reading was 56°, which matched Sept. 1921 for the mildest minimum reading for the month. (September's coolest reading is typically around 49°.) And only five days had lows in the 50s, which was well below the average of 13. Finally, the month joined Sept. 1968 and 1921 as the only Septembers to have no high temperatures cooler than 70°. A typical September sees five or six such days. Other interesting facts:
- Nine days had mean temperatures (average of the high/low) that were 10 degrees or more above average, but that was no match for the 14 such days in Sept. 1961. (1961's average high was just 0.1 degree lower than 2015, but 2015's average low was 1.7 degrees milder.)
- This September matched that of 2005 by having just one day with a below average mean temperature. However, in 2015 that day was just one degree below average while 2005's was four degrees below the norm. (And Aug. 2015 had only a handful of days that were below average, and they were all also just one degree below average.)
- This was the first time since 1998 that September was warmer than June, which was close to average (74.4 vs 71.2).
- Despite this year's record warmth, Sept. 1961 had more 90-degree days (8 vs. 6) while Sept. 2005 had more 80-degree days (23 vs. 19).
- The hottest high temperature of the year occurred on 9/8 when the mercury reached a record 97°. (However, the year's highest mean temperature occurred on 7/20, with a high of 94°/82°).
- The month saw the end of the longest streak of 80-degree days on record, 62 days. Then shortly thereafter another warm temperature record was established - most total days of 80°+ in a year (which grew to 114 days by the end of the month). In both instances the previous record holder was 1944. (Despite this record number of 80-degree days, 2015 ranks 12th for most lows of 70° or warmer.)
- The month was on the dry side and featured a 15-day stretch with no rain (the second longest streak of the year). In total 3.28" of rain fell, with most of it falling on two days - a record 1.51" on 9/14 and 1.27" on 9/30. And although the month had below average rainfall (one inch below average), it had considerably more rain than any of the next eight warmest Septembers, which averaged just 1.58".
|10 WARMEST SEPTEMBERS|
|Source: NOAA Local Climatological Data|