Apex Wx

Overview: A sprawling and unusually strong area of high pressure remains the dominant weather feature across eastern Canada and much of the northeastern United States. Surface pressure near 1036 mb (30.59 inHg) over Quebec is impressive for late September, and the broad ridge extends well southward along the East Coast. This strong high is maintaining a very dry air mass across northern Maine, with generally clear skies, light winds, and large differences between daytime and nighttime temperatures.

For Fort Kent and the Saint John Valley, abundant sunshine will allow temperatures to moderate considerably during the day, especially Thursday and Friday. At night, however, clear skies, dry air, and light winds will promote rapid cooling. Temperatures may approach freezing in colder locations tonight, bringing the potential for patchy frost and localized river-valley fog.

The strength and persistence of the high will also influence a developing coastal storm later this week. Rather than allowing the storm to move freely northeastward through New England, the blocking high over Quebec should help keep it farther south and east. Rain and stronger winds are increasingly likely across Downeast Maine and southern New England, while northern Maine should remain largely dry through Friday. Northeast winds may gradually increase as the pressure difference between the high and coastal low strengthens.

Wednesday: After the very chilly start, abundant sunshine should produce a substantial recovery. Expect a high in the lower to middle 60s, with light northerly winds. Humidity will be quite low during the afternoon. Clear skies and light winds return tonight, allowing temperatures to fall rapidly after sunset. Lows generally in the lower to middle 30s, with colder sheltered locations near freezing. Patchy frost and localized river-valley fog are possible.

Thursday: Sunny to mostly sunny and appreciably warmer. The modifying high and light winds should allow temperatures to reach the upper 60s to around 70°F, locally perhaps a little warmer in favored Valley locations. Thursday night remains mostly clear to partly cloudy, with lows in the upper 30s to around 40°F. Patchy late-night valley fog remains possible.

Friday: Mostly sunny to partly sunny and mild, although increasing northeast flow associated with the offshore storm may introduce somewhat more cloudiness. Fort Kent should remain north of the meaningful precipitation shield. Expect highs in the upper 60s to lower 70s, with northeast winds generally around 5–10 mph. Friday night trends somewhat milder, with lows likely in the lower to middle 40s.

Saturday, September 26 – Tuesday, September 29

Overview: The unusually strong high pressure system dominating Quebec and the Northeast during the previous forecast period will gradually weaken and retreat northward this weekend. Meanwhile, a developing coastal storm will become nearly stationary near southern New England and the western Atlantic. The persistent high to the north should help keep the storm and its more significant rain and wind south of northern Maine, although clouds associated with the system may occasionally reach the Saint John Valley. The coastal low is expected to linger through much of the weekend before slowly weakening.

Saturday should remain mild and mainly dry across Fort Kent and northern Aroostook County, with a mixture of sunshine and clouds. More cloud cover is expected Sunday as moisture increases aloft, but significant rainfall remains unlikely this far north. By Sunday night into Monday, a weak disturbance moving through the northern stream should bring somewhat cooler air and continued variable cloudiness.

Monday presently appears to be the coolest day of the period. By Tuesday, the air mass should begin to moderate again, allowing temperatures to recover somewhat. Overall, the Saint John Valley should remain on the quiet northern side of a much more active coastal weather pattern.

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. 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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