Apex Wx

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Overview: The slow-moving upper-level system responsible for the recent unsettled weather will continue moving farther into the Maritimes today. A few showers may linger near the Maine–New Brunswick border this morning, but drier air and increasing sunshine should gradually spread across Fort Kent and the Valley. North winds will remain noticeable, with occasional gusts around 20–25 mph.

High pressure will bring dry and pleasant weather for Labor Day, with abundant sunshine, comfortable humidity, and temperatures warming into the 70s. A weak disturbance crossing northern Maine Monday night into Tuesday will bring additional clouds and perhaps an isolated shower, but little moisture is associated with this system. Tuesday will turn cooler again, with mainly dry conditions and increasing sunshine. The next opportunity for widespread rain arrives Wednesday night into Thursday.

Sunday: A much-improved end to the holiday weekend as the upper low moves farther into the Maritimes. Morning clouds and perhaps an isolated shower near the international border should give way to increasing breaks of sunshine. Highs should reach the mid-60s, with north winds around 10–15 mph and gusts up to 25 mph. Sunday night should become mostly clear and cool, with northwest winds around 5–10 mph and lows in the mid-40s. Patchy Saint John River valley fog may develop in sheltered locations where winds become sufficiently light.

Labor Day: The best weather of the holiday weekend is expected as high pressure takes greater control. Sunny skies, dry conditions, and comfortable humidity should accompany a substantial temperature rebound, with highs reaching the mid-70s across the Valley. Northwest winds around 10–15 mph will keep the air well mixed. Monday night turns partly cloudy as the next weak disturbance approaches, with a 20% chance of a shower. Northwest winds should ease to 5–10 mph, with lows in the mid-40s.

Tuesday: A cooler day follows as weak shortwave energy crosses northern Maine. Some clouds are likely, especially earlier in the day, but substantial dry periods and increasing sunshine are expected, with only a small chance of an isolated shower. Highs should reach the lower to mid-60s, with west to northwest winds generally around 5–10 mph. Tuesday night should be mostly clear early before some clouds return, with winds becoming light and lows falling into the lower 40s, with locally colder conditions possible in sheltered Valley locations.

Wednesday, September 9 – Saturday, September 12

Overview: After the mainly dry and cooler weather expected Tuesday, the next significant change arrives Wednesday as a stronger low-pressure system approaches northern Maine from the west. Wednesday should begin dry, but clouds will thicken and rain will develop later in the day before becoming widespread Wednesday night. Southerly winds will also strengthen as the system approaches.

Rain will continue into Thursday, becoming more showery as the associated front crosses the region. An isolated thunderstorm is possible, and winds may become gusty as they shift to the west and northwest behind the system. The exact timing and track remain somewhat uncertain and will influence rainfall duration, wind strength, and thunder potential. Cooler and drier air returns Thursday night into Friday, with increasing sunshine Friday. High pressure should then provide a quiet and seasonably cool start to the weekend Saturday.

Wednesday: A mainly dry start should give way to increasing clouds as the next system approaches from the west. Rain chances increase during the afternoon, with highs in the mid- to upper 60s. Winds should become southerly around 5–15 mph. Rain becomes widespread Wednesday night and may be moderate at times as southerly winds strengthen. Lows should remain relatively mild in the lower 50s. NWS currently places precipitation chances near 100% overnight across Northwest Aroostook.

Thursday: A wet and increasingly breezy start is expected as the Canadian low and associated frontal system move through the region. Periods of rain should continue during the morning, becoming more showery with time. An isolated thunderstorm cannot be ruled out. Highs should reach the upper 60s to around 70°F, depending on frontal timing. Winds will shift from south or southwest to west and northwest behind the front, with gusts potentially reaching 30–35 mph. Showers diminish Thursday evening, followed by partly cloudy and cooler conditions overnight. Lows should fall into the lower 40s.

Friday: A distinctly cooler day follows the frontal passage. Lingering clouds should gradually give way to increasing breaks of sunshine as high pressure begins building toward northern Maine. Highs should reach only the upper 50s to around 60°F, with a northwest breeze making the change from Thursday particularly noticeable. Friday night should become mostly clear with winds diminishing and lows around 40°F, with locally colder conditions possible in sheltered Valley locations.

Saturday: High pressure should provide a quiet start to the weekend. Mostly sunny to partly cloudy skies and dry conditions are favored, with temperatures recovering somewhat into the mid- to upper 60s. Winds should be considerably lighter than Thursday and Friday. Saturday night should remain mainly clear and cool, with lows likely in the lower to mid-40s and some potential for patchy fog where winds become light.

The latest Climate Prediction Center outlook favors below-normal temperatures and above-normal precipitation across northern Maine, including the Saint John Valley. Troughing over eastern Canada should maintain a cooler pattern across northern New England while ridging strengthens farther south and west. Early to mid-September climatology across the Valley generally features daytime highs in the mid-60s and overnight lows in the lower to middle 40s, with temperatures gradually declining through September.

Outlooks updated 7-9 AM weekdays & 8-10 AM weekends and holidays. Long range outlooks indicate broader temperature and precipitation trends rather than precise day-to-day forecasts.

Updated every 3-6 hours from NWS Caribou

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.

How accurate are forecasts?

Forecast confidence generally decreases as lead time increases. Forecasts for the next few days usually provide considerably more detail and confidence than forecasts a week or more in advance. Beyond about 7 days, forecasts are most useful for identifying broader weather patterns and temperature or precipitation trends rather than predicting exact conditions at a particular place and time.

Individual computer-model runs—especially those depicting specific storms, snowfall amounts, or other details a week or more in advance—should not be treated as forecasts by themselves. Extended forecasts will change as new observations become available and models better resolve the evolving atmospheric pattern. Check updated forecasts as the event approaches.

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