Apex Wx

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Wed. Sep. 2 – Fri. Sep. 4
High pressure will keep the Saint John Valley dry and pleasant through today, with seasonable temperatures and a mixture of sunshine and clouds. The pattern changes tonight as high pressure moves into the Maritimes and a low-pressure system approaches from Quebec. Clouds will thicken, with rain spreading into northern Maine overnight.

Thursday will be the wettest day of the period, with widespread, steady rain continuing through much of the day and into Thursday evening. The rainfall should provide some beneficial moisture, with flooding not expected. As the system moves into the Maritimes Thursday night, the steady rain will taper to showers. Friday remains unsettled beneath the lingering upper-level disturbance, with scattered showers most numerous across northern Maine. An isolated afternoon thunderstorm is possible before conditions gradually improve.

Wednesday: Patchy early-morning fog will give way to mostly sunny and pleasant conditions. Temperatures should climb to around 72°F, with southeast winds generally 5–10 mph. Clouds will increase this evening and overnight as the approaching system draws closer. Rain should begin spreading into the Saint John Valley late tonight toward Thursday morning, with a low in the lower 50s.

Thursday: Cloudy, cool, and wet with rain likely throughout much of the day. Periods of moderate rain are possible as the developing low and occluded front cross the region. Temperatures will struggle to rise much beneath the clouds and precipitation, with a high around the middle 60s. Southeast winds near 10 mph may occasionally gust around 20 mph. Rain continues Thursday evening before gradually becoming more showery overnight as the surface low moves toward the Maritimes. Low in the middle 50s.

Friday: The widespread steady rain will have ended, but the weather will remain unsettled as the departing surface low and lingering upper-level trough maintain scattered to numerous showers, particularly across northern Maine. An isolated afternoon thunderstorm is possible. Some brighter intervals may develop between showers, allowing temperatures to recover into the upper 60s. Winds will become north to northeast later in the day. Showers remain possible Friday night, with a low in the upper 40s.

Sat. Sep. 5 - Tue. Sep. 8

The unsettled weather will linger into Saturday as the late-week storm system slowly pulls away into the Canadian Maritimes. A disturbance rotating around the departing system will keep scattered showers possible, especially during the afternoon, while brisk north to northeast winds make the day feel somewhat cooler.

Conditions improve Saturday night into Sunday as drier air and high pressure begin building into northern Maine. Sunday should be mostly sunny and seasonably cool, followed by an even nicer Labor Day as high pressure settles across the region. Sunshine and lighter winds should allow temperatures to recover into the lower to middle 70s Monday. The next disturbance approaches Monday night, bringing only a slight chance of a shower. Current guidance favors mainly dry and seasonable weather Tuesday, although the timing of the next system remains somewhat uncertain.

Saturday: Partly to mostly cloudy and breezy with scattered showers, particularly during the afternoon as another disturbance rotates around the departing Maritimes low. Temperatures should remain cool, with a high in the middle 60s. North to northeast winds around 10–15 mph may gust to around 20–30 mph. Shower chances diminish Saturday evening as the system begins pulling away, followed by mostly cloudy to partly cloudy skies. Low in the lower to middle 40s.

Sunday: A noticeable improvement as the upper low moves farther into the Maritimes and drier air spreads into northern Maine. Expect partly to mostly sunny skies with a seasonably cool high in the upper 60s. Northerly winds may remain somewhat noticeable early before gradually easing. Sunday night should be partly clear and cool, with a low in the lower to middle 40s.

Labor Day: High pressure should provide the best weather of the four-day period, with mostly sunny skies, dry conditions, and temperatures recovering into the lower 70s. Winds should be considerably lighter than during the weekend. Clouds may begin increasing Monday night as the next disturbance approaches from the west, with a slight chance of a late shower. Low in the middle to upper 40s.

Tuesday: The forecast becomes less certain as another disturbance approaches northern Maine. Current guidance favors a mixture of sunshine and clouds with scattered showers possible, rather than an all-day rainfall. Temperatures should remain seasonable, with a high around the upper 60s to near 70°F. The timing and coverage of showers will depend upon the evolution of the approaching frontal system and should become clearer in subsequent forecasts.

The latest Climate Prediction Center outlook indicates equal chances of above-, near-, or below-normal temperatures and precipitation across northern Maine during the period. This reflects increased uncertainty in the weather pattern rather than a forecast for near-normal conditions. Across the Saint John Valley, early to mid-September climatology generally features daytime highs in the mid-60s and overnight lows in the lower to middle 40s, with temperatures gradually trending downward as September progresses

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.