Apex Wx

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Thursday, September 17 – Saturday, September 19

Overview: High pressure and weak winds will keep Thursday relatively quiet across the Saint John Valley after any early river-valley fog dissipates. A developing low-pressure system will bring more substantial rain to southern and coastal Maine tonight, but the deeper moisture should remain well south of the Valley, leaving northern Aroostook County, including Fort Kent and vicinity, largely dry.

A cold front and upper-level trough will cross northern Maine Friday, bringing a few light morning showers before much cooler and drier air arrives. The more significant impact will be strengthening northwest winds as colder air and daytime mixing allow gusts to reach 30–40 mph. NWS Caribou notes that isolated tree damage or power interruptions are possible, particularly with trees still carrying much of their foliage. Winds will gradually diminish Friday night as the system moves east. High pressure builds toward the region Saturday, bringing a sunny, dry, and cool start to the weekend with considerably lighter winds.

Thursday: Patchy early-morning valley fog will dissipate, followed by partly sunny to occasionally mostly cloudy skies. Despite the major rain-producing system passing through southern and coastal Maine, Fort Kent and vicinity should remain dry. Temperatures will reach the mid- to upper 60s, near to slightly above normal, with light and variable winds. Tonight will be mostly cloudy to partly cloudy with patchy fog redeveloping after midnight. Lows will fall into the mid- to upper 40s, with calm winds.

Friday: Patchy early fog will give way to mostly sunny skies, although a 30% chance of light showers remains mainly before noon as the cold front and upper trough cross northern Maine. Highs will reach only the upper 50s to around 60°F. The primary concern will be the wind rather than precipitation. Northwest winds will increase to 15–20 mph during the afternoon, with gusts around 35–40 mph. Isolated tree damage or power interruptions are possible, particularly with trees still substantially leafed. Friday night becomes mostly clear and chilly. Northwest winds remain gusty during the evening before gradually easing, with lows around the upper 30s to 40°F.

Saturday: High pressure building toward the region will provide a sunny, dry, and cool start to the weekend. Highs should reach only the upper 50s, several degrees below normal. Northwest winds around 5–10 mph may still gust near 20 mph, but conditions will be considerably less windy than Friday. Saturday night turns partly cloudy as winds become calm, allowing temperatures to fall into the mid- to upper 30s. Sheltered portions of the Valley could again approach temperatures favorable for localized frost, although the extent will depend on cloud cover and how efficiently temperatures fall after sunset.

Sunday, September 20 – Wednesday, September 23

Overview: After the cool, dry weather Saturday, high pressure will begin shifting east Sunday as a weak disturbance approaches northern Maine. Clouds will increase, with a slight chance of light showers developing during the afternoon and lingering into the evening. Moisture remains limited, however, so most of the Valley should stay dry and rainfall amounts should be light.

Weak high pressure returns Monday and should remain influential through midweek, bringing an extended stretch of mainly dry weather. Sunshine becomes more prevalent Monday and Tuesday, while temperatures gradually moderate from around 60°F Monday into the lower 60s Tuesday and mid-60s Wednesday. Nights will remain chilly under light winds and partial clearing, with temperatures generally falling into the mid- to upper 30s. Sheltered valleys may therefore experience localized frost where skies clear sufficiently and winds become calm. Wednesday remains dry and somewhat milder, followed by partly cloudy skies Wednesday night.

Sunday: After a chilly start, clouds will increase as the weak disturbance approaches. Skies should be partly sunny to mostly cloudy, with a 20% chance of showers developing during the afternoon, mainly after early to mid-afternoon. Much of the day should remain dry. Highs will reach the upper 50s to lower 60s, with light southerly winds. A slight chance of showers continues into Sunday evening before ending, followed by mostly cloudy skies. Lows will fall into the upper 30s.

Monday: Weak high pressure returns behind Sunday’s disturbance, bringing a mainly dry and brighter day. Mostly sunny skies are expected, with highs around the upper 50s to lower 60s. Winds should remain light. Monday night will be partly cloudy with lows again in the mid- to upper 30s. Sheltered portions of the Valley may need to be watched for localized frost if skies clear sufficiently and winds become calm.

Tuesday: High pressure remains in control, providing another dry day with mostly sunny skies. Temperatures should recover slightly into the lower 60s, near seasonal levels. Tuesday night will be mostly clear with lows in the mid- to upper 30s. The combination of clear skies and light winds could again support localized frost in colder low-lying areas.

Wednesday: The quiet pattern continues as high pressure remains influential across northern New England. Sunny skies are currently expected, with temperatures moderating into the mid-60s, making Wednesday the mildest day of the period. Wednesday night will become partly cloudy, with temperatures falling into the upper 30s.

Long Range: Thursday, September 24 – Wednesday, September 30

The outlook for the period favors above-normal temperatures and equal chances for precipitation along the northern Maine border. Broad ridging across eastern North America supports the warmer tendency, while equal chances means CPC does not favor a wetter, drier, or near-normal precipitation outcome. Normal temperatures across the Saint John Valley during this period are generally near 60°F for daytime highs and in the upper 30s to around 40°F overnight.

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.

Weather Apps

Most weather apps rely heavily on automated forecast data. They can be useful for a quick look at routine weather, but automated forecasts may miss important local details or the significance of rapidly changing conditions. During hazardous or changing weather, consult weather.gov and other official National Weather Service information rather than relying solely on an app.

Radar Apps

Weather radar is an invaluable tool for tracking precipitation and storms, but radar images should not be interpreted as a real-time picture of conditions at the ground. Data collection, processing, transmission, mosaicking, and app updates can introduce delays, and radar detects energy returned from precipitation at varying heights above the surface. During rapidly developing or moving storms, conditions at your location may therefore differ from what a radar app appears to show. Use radar together with current observations and official National Weather Service warnings.