Welcome back to our Boston Globe Weather Mailbag, where we sift through readers’ weather questions and answer them weekly. You can submit questions on everything from “Does it snow in May?” to “What’s up with El Niño?” — and everything in between.
Every other week, I’ll take your questions and answer them as a way to best address what’s on readers’ minds. Many of your questions may also turn into more in-depth stories for our team to tackle in the future.
This week’s weather mailbag includes topics on fall foliage and when to start leaf-peeping to check out the autumn colors, why smoky skies lead to red sunsets, and why allergies seem to be worse in August.
So let’s get to it.
Q: When can we expect the leaves to start turning their colors? I’m looking forward to fall and want to plan my trips for leaf-peeping accordingly.
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— Meredith R., Andover, Mass.
A: Between the drop in daily average temperatures and the waning hours of daylight, there are a couple of signals during fall that will influence trees to stop food production. This will, in turn, result in chlorophyll breaking down. Chlorophyll is the reason why leaves are green and plays a big role in converting sunlight into energy for plant growth, absorbing many other wavelengths and emitting the green light. When the chlorophyll begins to breaks down, you start to see the changing of colors from a deep green to more bright red, yellow, and oranges.
In New England, we typically see this foliage process begin around mid-September across the northern tier of the region. For Massachusetts, colors will begin to change around the first couple weeks of October. The color changes happen relatively quickly, with peak foliage season usually occurring during the second half of October. Of course, the farther north you go, the earlier foliage and peaking begins.
Typically by the beginning of November, many of the leaves will have turned to brown and will begin to fall to the ground.
Q: Why do hazy or smoke-filled skies make the sunsets red? Is it because of the color of the sun?
— Jeremy L., Boston
A: It’s not the color of the sun responsible for the red skies in a smoky atmosphere, but really how our atmosphere interacts with the incoming sunlight. It’s common to see a red tint during sunrises and sunsets when smoke is hovering above.
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Smoke particles are larger than average air molecules and do a great job of scattering light, especially longer wavelengths of red and orange for long distances. These longer wavelengths overcome the typical blue skies hue that regular air molecules scatter.
In the visible light spectrum, blue light is a shorter wavelength and may not be seen to the naked eye as easily with smoke present as those longer wavelengths — thus red is what we see.
Q: Why does it feel like allergies always get worse in August? My allergies seem to heighten late August and September.
— Michele O., Lunenburg
A: You’re on to something. Allergy sufferers can experience all sorts of challenges throughout the year due to a wide variety of culprits — pollen, dust, mold, and other air pollutants. However, August is generally the most active month of the allergy season. And that’s the case for a few reasons.
The main being that August usually sees a rapid rise in ragweed and other weed-related pollen while grass pollen is still very prominent throughout the region. This provides a daily one-two punch for allergy sufferers. And with warm temperatures in August, pollen spores can travel far and wide.
Another allergen very common in August is mold. With enough time passing with increased summer temperatures and humidity, by the time August rolls around, mold spores float pretty far both indoors and outside. With the help of humidity and moisture levels, mold can take hold in soil, plants, and on or within structures. This can mean little to no relief for folks who are sensitive to mold, especially if there is some present within the home — one can hardly catch a break from the allergen.
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Ken Mahan can be reached at ken.mahan@globe.com. Follow him on Instagram @kenmahantheweatherman.