Special Weather Discussion

Latest Weather Discussion by Kyle Elliott

* another long stretch of dry, quiet and pleasant weather *

10:30 a.m. Tuesday, September 30, 2025:

Since September 10, the weather has been persistently warmer-than-average across the mid-Atlantic States. There have not been any 90-degree days this month at Millersville University, but high temperatures failed to reach 75°F on only 5 occasions (9/10, 9/16-17, 9/21, and 9/24). In addition, overnight lows have trended UPWARD during a month where the average low decreases by 12°F. In fact, the mercury has not fallen below 60°F at the 'Ville since September 22, and that morning's low was still a balmy 59°F. In keeping with the trend, September will end on a pleasantly warm note today despite a thick veil of cirrus clouds across the sky. High temperatures should reach the upper 70s to perhaps 80°F across northern MD, southeastern PA and the Lower Susquehanna Valley, but it won't be as humid with dewpoints in the 50s. Southerly flow in the upper-levels of the atmosphere is drawing the deck of clouds associated with Hurricane Imelda northward into the region. However, the clouds will gradually thin out this afternoon and then disappear completely later tonight as Imelda accelerates northeastward into the central Atlantic.

A "backdoor" cold front.. or one that moves from northeast-to-southwest instead of northwest-to-southeast.. will slide through the Lower Susquehanna Valley later tonight. Behind it, north-northeasterly winds of 8-16 mph will usher a slightly cooler and much drier air mass into the region on Wednesday. High temperatures will peel back to around average (low 70s) despite perfectly sunny skies, and dewpoints should tumble into the upper 30s or low 40s by the afternoon hours (see below). Low temperatures should still be above average tonight and in the comfortable low-to-mid 50s, but that will change during the rest of the week.

A massive high pressure system of Canadian origin will settle into the Northeast, Delmarva Region and western Atlantic late this week and then hold its ground through early next week. As a result, we'll get to enjoy another extended period of mostly sunny, dry and beautiful weather and finally experience a true taste of fall (see below)! High temperatures should be in the upper 60s to perhaps 70°F on Thursday, in the low 70s Friday and mid-to-upper 70s Saturday. However, overnight lows should tumble into the crisp low-to-mid 40s both Wednesday and Thursday nights due to efficient, radiational cooling. Dewpoints will hover in the upper 30s to mid 40s through Friday, and winds will also subside late this week. Thus, it's certainly possible that the mercury bottoms out at 39-40°F on the "coldest thermometers" in the most outlying areas Wednesday and/or Thursday nights. It won't be quite as chilly Friday night, but lows should still bottom out in the mid-to-upper 40s outside of urban centers. If you're eagerly anticipating the arrival of "sweater weather," the wait is finally over! A gradual warming trend will take place from Saturday into early next week, but overnights should remain quite comfortable and humidity rather low with both low temperatures and dewpoints in the 50s from Sunday-Tuesday. A light, south-to-southwesterly breeze is expected to return on Saturday and stick around through early next week, so high temperatures will likely be back in the upper 70s to perhaps 80°F on Sunday and low 80s next Monday and Tuesday.

You really couldn't ask for better conditions during the first week of October, and homecoming festivities at Millersville and other universities around the region won't be impacted by adverse weather this year. You will probably need a jacket during the Homecoming Parade from 8:30-10:00 AM Saturday morning but should feel comfortable in light clothing during the afternoon hours. Enjoy the festivities and beautiful weather over the weekend! -- Elliott