Weather in Bar Harbor in September

Prime time. September is about as good as Bar Harbor gets. Highs average 19.3 °C, lows 11.7 °C, and rain falls on 10 days — nothing in the month is working against you.

September ranks 2 of 12 in Bar Harbor. Only August scores clearly higher, and the difference is small enough to be settled by price rather than weather.

Rain on 10 days, 3 of them heavy. Enough to need a plan B, not enough to need a plan around it. Nothing specialised needed — this is the month you pack for the trip rather than for the weather.

What the averages hide

Averages flatten a month, and this one hides a few things: it never really gets hot: not one day in an average September reaches 30 °C. Across the twenty years measured, the hottest September day reached 31.7 °C and the coldest night fell to 4.4 °C, and the wettest single day dropped 100 mm — roughly 100% of the month's rain in one day.

September is moderately variable: 40 mm in the driest year against 205 mm in the wettest, around an average of 100 mm. Roughly two Septembers in three land near that average, and the third does something else entirely.

Wind is light at 5.2 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 83%, high enough to notice on the warm days without dominating them.

How September sits in the year

The month is on the way down: 3.1 °C cooler than August, with October dropping another 5.8 °C. The first week and the last are not the same trip.

Daylight in September

12.6 hours of daylight, losing 1.5 hours across the month. That is between Bar Harbor's extremes of 15.5 and 8.9 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 14 °C in September — cold — a quick dip rather than a swim, and a wetsuit if you are in for longer. This is the warmest the water gets all year.

How busy it gets

Peak season. Expect the highest prices of the year and to be booking well ahead.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

September in Bar Harbor versus nearby

If Bar Harbor is one option among several, the nearby comparison is worth making. Sherbrooke is close enough to be a coin toss — within a degree on temperature, 4 days more rain. Boston is close enough to be a coin toss — 5 °C warmer, 1 day less rain.

So: September is effectively as good as it gets here — 0 points behind August, which is inside the margin where the weather stops being the deciding factor and price starts being it.

Every month in Bar Harbor

See all twelve months in Bar Harbor, or where else to go in September.