Q: I was just wondering if we are having more humid days than in the past years?
It seems like five to 10 years ago, we didn’t have this humid weather.
A: In my decades of work talking about the weather to the public, I have made one strong observation. When it comes to weather events, the most recent always seems the harshest. For example, some people say they never have remembered as much snow or cold in decades compared to last winter.
Or that we’ve never had as much rainfall as we did in June.
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However, when it comes to your case, you do have some merit. Last month, according to my records here at the station, the average dewpoint temperature (the best measure of comfort and humidity) was 61 degrees. This marks the highest dewpoint for the month of June over the past 10 years.
Is this a continuation of a more consistent long-term trend? Not quite.
A couple of years ago, we had our lowest average June dewpoint, which was 55 degrees.
Therefore, June was a case of a wet month, but not an overall higher trend compared to a decade or two ago. As an added note, once we are in a wet and humid pattern, it’s hard to break. With more moisture in the ground and air, we have more fuel for showers and thunderstorms. These showers and thunderstorms then replenish the ground. Therefore, our humid June has led into a humid July despite a couple of brief breaks of drier polar air from Canada.
Q: When lighting strikes a tree, based on some videos I’ve seen, the tree doesn’t catch fire but rather just seems to split. Why?
A: Lightning is very hot — thousands of degrees. But it’s also quite fast.
Sometimes the lightning is enough to ignite the wood, especially when there is not much rainfall in the thunderstorm. This is why lightning is ranked fairly high behind humans as a cause of major wildfires.
Sometimes, the heat is too fast and just leaves a scorch mark on the tree without igniting the wood. Many trees also are split by lightning, and some witnesses even report the tree exploding.
What happens in these cases is the lightning and resistance to the flow of electricity heats the moisture and sap in the tree. The heated sap and moisture expands to steam, which creates enough pressure to split the tree apart.