Apex Wx

Overview:High pressure that brought Saturday’s dry weather is shifting east into the Maritimes today as a weak low-pressure system and cold front approach northern Maine. Southerly flow ahead of the system will increase clouds and moisture across the Saint John Valley. Most of Sunday morning and early afternoon should remain dry, with showers becoming more likely later in the day and especially during the evening. Limited moisture and instability should keep rainfall light and rule out any meaningful thunderstorm threat.

The cold front will move east Monday morning, although lingering low clouds, patchy fog, or an isolated shower may persist early. Cooler and drier northwest flow will then develop behind the front, allowing clouds to gradually break while northwest winds become somewhat breezy during the afternoon.

Canadian high pressure builds closer Monday night and settles across the region Tuesday, bringing clearing skies, lighter winds, and another stretch of dry weather. The combination of clear skies and diminishing winds will also favor strong nighttime cooling, with temperatures falling well into the 30s. Patchy frost may develop in colder sheltered portions of the Valley Monday night, with frost potential continuing Tuesday night.

Sunday: Clouds will increase rapidly this morning, resulting in a mostly cloudy day. Much of the morning and early afternoon should remain dry, with showers becoming more likely later in the afternoon as the approaching front draws closer. Highs should reach the upper 50s, with southerly winds generally around 5–10 mph. Showers are most likely Sunday evening and early Sunday night before gradually diminishing toward morning. Rainfall should remain light, generally around 0.10 inch or less. Lows will fall into the upper 30s, with patchy fog possible overnight.

Monday: A lingering shower or patchy fog may remain possible early as the front moves east, but most of Monday should be dry. Clouds will gradually break for some sunshine as cooler and drier air arrives. Highs should reach the mid-50s. Northwest winds increase during the day and may gust around 20 mph. Monday night becomes mostly clear and chilly as high pressure builds closer, with lows falling into the mid- to upper 30s. Patchy frost may develop in colder sheltered areas.

Tuesday: High pressure will provide a sunny, dry, and seasonably cool day. After another chilly start, temperatures should recover into the upper 50s to near 60°F, with light northerly winds. Tuesday night should remain mostly clear and cold, with temperatures falling into the mid-30s. There is a chance of frost where winds become calm and efficient nighttime cooling develops.

Wednesday, September 23 – Saturday, September 26

Overview: Following the cool and dry weather expected Tuesday, Canadian high pressure will remain the dominant influence across northern Maine Wednesday and Thursday. Mostly sunny skies, light winds, and a gradually moderating air mass should allow daytime temperatures to climb from the lower 60s Wednesday into the mid- to upper 60s Thursday. Clear skies and light winds will still favor chilly nights, with temperatures falling into the 30s and some frost possible in colder sheltered locations.

Forecast confidence decreases Friday into Saturday as an upper-level trough may evolve into a cut-off low near the Mid-Atlantic or Northeast. Current model guidance agrees on the general development of this feature but differs on its location, strength, and evolution. Those details will determine how far north its associated clouds and precipitation extend.

For now, current NWS guidance keeps the Saint John Valley mainly dry through Saturday. Some increase in cloud cover is possible late in the week, but significant rainfall is not indicated at this time. Temperatures should remain relatively mild for late September, generally reaching the mid-60s during the afternoon.

Wednesday: High pressure will provide a sunny and dry day after a chilly start. Temperatures should reach the lower to mid-60s, with light winds. Wednesday night will be clear and cool, with lows in the mid-30s around Fort Kent and potentially somewhat colder readings in sheltered locations. Patchy frost may be possible where temperatures fall efficiently after sunset.

Thursday: Sunshine continues as high pressure remains dominant. Temperatures should moderate noticeably, reaching the mid- to upper 60s, making Thursday the mildest day of the period. Winds remain light. Thursday night should be mostly clear to partly cloudy, with lows in the upper 30s to around 40°F.

Friday: The forecast becomes somewhat less certain as the eastern U.S. trough and developing surface system begin influencing New England. Current guidance nevertheless keeps Fort Kent and the Saint John Valley predominantly dry, with partly to mostly sunny skies and highs in the mid- to upper 60s. Clouds may increase later in the day and Friday night, when lows should fall into the upper 30s to lower 40s. Precipitation probabilities remain low at this point.

Saturday: The position of the late-week system will remain important in determining the northern extent of cloud cover and any precipitation. Current guidance continues to favor mainly dry conditions across northern Maine, with partly sunny skies and highs generally in the mid-60s. Saturday night will be partly cloudy and milder than earlier in the week, with lows in the lower 40s.

Weather Notice

Apex Wx forecasts are based on available observations, computer model guidance, and other meteorological data. Conditions and forecast guidance can change, and information displayed here may not reflect the latest official forecast or warning information. Always visit NWS Caribou for the latest official forecasts, watches, warnings, and advisories for northern Maine.

Apex Wx is a private weather information service unaffiliated with NOAA or the National Weather Service and operated by Joseph Becker, PhD. Dr. Becker earned a Certificate in Weather Forecasting from Penn State University and is a trained NWS SKYWARN Storm Spotter.

Credits

• Sun and Moon data from the U.S. Naval Observatory, with additional astronomical information from timeanddate.com.
• NOAA warning banner provided by WillyWeather.com.
• Through December 2026, additional archived Apex Wx weather data are available through the University of Utah's MesoWest.
• Current and archived Apex Wx weather data are available through Synoptic Data, the successor to MesoWest.
• Apex Wx logo by Joanna Becker © 2016. Visit Bushi and Brush Arts Dojo.

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