Information For Autumn

2019-09-23 05:30:06.000 – Ryan Knapp, Weather Observer/Staff Meteorologist


Autumn has arrived and like usual, we have been receiving inquiries about foliage and the operating hours of the summit. I thought I’d take a minute to address these two items so you might be better informed for the days and weeks ahead.
When will we see peak foliage? To be honest, your guess is as good as ours as there is no set day/week and things can vary from location to location and from year to year. A great example of this is a post that NWS, Caribou does each year on or around October 2nd. The series of images are from a camera at Hanson Lake by the Presque Isle airport and shows the amount of change that has occurred on the same date at the same location over six years.

As you can see, things can vary greatly from one year to the next. One reason for the variation is weather as it factors into the colors you will see and when you will see them. A late spring or an overly wet summer can delay when color starts to show. If summer is on schedule though, adequate rainfall is important as this keeps trees healthy and aids in their leaf retention. Whereas a drought period in the summer can cause stresses that result in trees losing their leaves or change their colors early. As we head into fall, the best conditions to hope for are cool, dry, and sunny conditions. The sunny skies promote sugars in the leaves. Then the cool air, especially during the night time hours, allows the veins in the leaves to constrict and the sugars become trapped in the leaves promoting the formation of red, purple, and crimson pigments. While cool weather is good for autumn colors, freezing conditions are bad as frost and/or freezing conditions can result in the color change to be halted and/or result in a premature end to the season as leaves turn brown and start to fall. Wind and rain can also result in a premature end to the season as both of these can result in the leaves getting knocked off prior to fully developing their colors. And while warm days might make leaf peeping more enjoyable for people, warm days can actually reduce the intensity of the colors. So when it comes to weather, a lot of factors have to come together and depending on how and when those factors come together, it’s partly why colors and peak occurrence dates can vary from year to year. (If interested in learning even more about the science behind autumn foliage color, Harvard Forest is a great resource to get you started in your exploration)
Fall colors typically start in the north and high elevations in early to mid-September then gradually spreads southward through late Sept/Oct like a slow moving wave of sorts. The transition for the far north (think Pittsburg, NH) is already underway with several areas starting to approach peak color (at least from the pictures and reports I have seen). On the Presidential Range (where Mt Washington is located), colors are peaking at the 4000+ foot level (ie, treeline) and are starting to descend into the valleys around the summit. In the coming days, colors will start to peak around the base of the mountain, and then the wave of color will pass and continue southward in the coming weeks. Northern areas will then see the foliage falling off and leading into the “gray period” or “stick season” between fall and first snow. So, while peak color will vary, if you miss peak color in one area of the state/region, check around as there will be plenty of other areas you can still go to and experience New Hampshire’s foliage season.
For additional information, some great resources to check out are:
Additionally, if you Google “NH foliage” or “New England foliage” there are several other resources available to further assist you. Social media outlets like Twitter and Instagram are another great resource as you can seek out tags like “#nhfall” “#nhfoliage” or “#newenglandfall” for current images of conditions around the state/region.
If you plan to check out the foliage of the White Mountains by hiking, a weather forecast is important to check out in your planning as conditions can start to vary greatly from day to day and from base to summit where summits can start to experience full-on winter conditions. For expected weather 48 hours out, you can check our Higher Summits Forecast or, for a second opinion, NWS’s Recreational Forecast.
If Mt Washington is part of your fall foliage itinerary, it is important to check the various websites of the entities that share this mountain as shorter days and variable weather conditions (like snow) can affect their operations. You can find all their information at:

NH State Park

Most of them have additional information on their various social media outlets too. If, after checking their sites or social media outlets, you are still unsure, it is best to contact the various outlets directly to ensure you are getting the most out of your travel time in the White Mountains. Mount Washington Observatory operates independently, so any questions about operating hours and day to day operations should be directed towards one or more of the groups listed above so that you are getting the best and most relevant information on any given day. Lastly, just in case the weather limits or closes operations to/from/on the summit, as I tell my family and friends, when it comes to Mt Washington, always have a “Plan B” just in case.
Fall foliage in late September at treeline along the Mt Washington Auto RoadFall color along the Mt Washington Auto Road as seen Weds, Sept 18, 2019


Ryan Knapp, Weather Observer/Staff Meteorologist

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