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7-Day Outlook: August 29–September 4, 2026

A tranquil start to September is expected across the Saint John Valley as high pressure remains in control Tuesday and early Wednesday. Aloft, the flow will begin to transition as a low pressure system tracks eastward across Canada. The developing pattern will gradually return moisture and cloud cover to northern Maine, leading to a wetter period beginning late Wednesday or Thursday. NWS guidance continues to show some disagreement on the precise timing of the associated front, with recent trends favoring a somewhat slower progression.

Tuesday should be the quietest day of the period. High pressure centered over northern New England will provide a dry and relatively stable air mass, with mostly sunny skies and light, variable winds. After a seasonably cool start, temperatures will warm into the lower 70s in Fort Kent. With light winds and a dry boundary layer, the atmosphere should remain quite comfortable through the afternoon. Overnight, quiet conditions are expected with partly cloudy skies and lows in the upper 40s. Some patchy valley fog could again develop toward Wednesday morning.

Wednesday will begin quietly, but conditions should gradually deteriorate as the next low pressure system moves eastward through Canada and moisture increases ahead of its associated frontal system. Clouds will thicken from west to east, with rain showers becoming increasingly possible during the afternoon or evening. The principal forecast uncertainty at this point is timing. Current NWS guidance favors rain developing during the latter half of the day, with the greatest precipitation potential farther east across Maine. Wednesday's high will reach the lower 70s, with showers becoming likely Wednesday night as temperatures fall into the lower 50s.

Thursday currently appears to be the most unsettled day of the period. As the Canadian low and its associated trough and frontal system approach the region, periods of rain or showers are likely, although the exact timing and rainfall amounts remain uncertain as the system weakens while advancing eastward. For Fort Kent and the upper Saint John Valley, precipitation may be intermittent rather than a continuous soaking rain, with locally heavier showers possible as the frontal zone crosses. Temperatures should remain cooler, generally in the middle 60s, with clouds and precipitation limiting daytime warming. Thursday night will remain mostly cloudy, with temperatures falling into the lower 50s and a continued chance of showers.

Mostly cloudy skies will begin the day Friday, but increasing breaks in the clouds are possible during the afternoon as drier air gradually moves into northern Maine behind the departing frontal system. Temperatures should remain seasonably cool, with highs in the middle to upper 60s. Friday night will remain mostly cloudy, with a chance of lingering showers and lows in the lower 50s. How quickly conditions improve late in the period will depend on the eastward progression of the upper-level trough and associated surface low.

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: This information is based on available computer models and data and may not reflect current conditions or later forecast updates. Always visit NWS Caribou at https://www.weather.gov/car/ for the latest official watches, warnings, and advisories for northern Maine.

Credits

• Sun/Moon data from US Naval Observatory with additional information from timeanddate.com.
• NOAA Warning Banner provided by WillyWeather.com.
• Until Dec. 2026, additional Archived Weather Data from Apex Wx is at the University of Utah's MesoWest
• Apex Wx Weather Data at Synoptic Data (successor to MesoWest)
  
• Apex Wx logo by Joanna Becker ©2016 (Visit Bushi and Brush Arts Dojo)

How accurate are forecasts? On average, for the first 72 hours the accuracy is 90 percent. For days 4-7 it is 70 percent. After seven days, it is 50 percent—just good for indicating trends. On social media and other similar sites, posts that show a forecast model run a week out are just for clicks and likes, and are not considered reliable. Extended forecasts are subject to change as weather patterns evolve so should be considered guidance rather than precise predictions. Check for updated forecasts and advisories as conditions develop.