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Weather Mailbag: See an explosion of insects in your yard lately? Also, an interesting radar anomaly is explained.

– Roger F., Spencer, Mass. You're on to something here. Yes, the sudden burst of warm weather will signal many plants/weeds, insects, and in this case, arthropods, to kick things into gear and their numbers can multiply in just a short window. Many towns in Worcester County have seen multiple 80-degree weather days in April followed by pretty warm nights. I can imagine how much heat was retained under and around your carport from the very high sun angle this month, likely making it feel warmer in there despite what the thermometer suggests. Millipedes thrive in warm and humid environments. Humidity has still been somewhat representative of a typical spring, but there certainly has been more water vapor in the air than usual. Frankly, with March soaring over 4 degrees warmer than average and April running 1.3 degrees above average, there simply is more water vapor in the air that can promote population surges in certain insects. Advertisement Q: According to the US Drought Monitor, most of Massachusetts is currently in a drought, with the remainder showing unusually dry conditions. How do they measure that? Advertisement – Daniel Liss, Cambridge, Mass. That's right. At least some parts of Massachusetts have been in some level of drought since the third week of September 2024, a streak extending seven months. This is the longest stretch where at least moderate drought has been present in the state since an 11-month stint from June 2016 to May 2017. The good news is that Massachusetts and all of New England have made progress against drought conditions in the past month or so, thanks in part to the snowmelt from the winter. We're still in a precipitation deficit pretty much statewide, but no longer as extensive. There are a handful of data points that go into determining drought status. Precipitation, temperatures, streamflows, soil moisture, reservoir and lake/pond levels, vegetation health, and crop conditions are all considered. My favorite, and perhaps most important as we head toward summer, is evapotranspiration — the evaporation of water into the atmosphere from the ground or through vegetation. The data points derived from the above weather parameters are categorized in percentiles and then ranked — with the result determining whether or not the region is in a drought, and to what severity. Q: Why is there nearly always a precipitation 'shadow' over Berkshire County, especially when rain or snow approaches from the west? Looking at the radar, you can see the precipitation shield fade as it approaches from the Hudson River Valley. – John P., Dalton, Mass. This is a great question and not the first time I've been asked this. There are usually two things happening concerning precipitation entering the Berkshires from the west — and they both have to do with the geography. Advertisement Before I get into this, a quick definition first. A 'precipitation shadow' refers to one side of the mountain range (almost always the eastern side) seeing less precipitation than the other (the western side). The Hudson River Valley lies very flat, and whatever air that rises and condenses into snow, rain, or thunderstorms has a fairly unobstructed path in doing so. As the storm approaches the hills and mountains of Berkshire County, the wind flow at the surface is forced by the increasing elevation to rise faster, making the water vapor condense quickly as precipitation. By the time the wind reaches over the mountain peaks and to the eastern side, most of the water vapor has condensed out, leaving little to no precipitation left to fall. As warm, moist air hits a mountainside, it lifts and condenses, making more rain possible to fall with passing systems over Vermont and New Hampshire mountains. Saltwire The second point is that sometimes, if the base of the storm is low enough, precipitation shadowing can occur on the radar. The radar rotates 360 degrees many times per second to capture what is going on in the atmosphere. Think of a radar as a lighthouse, just extremely fast, picking up what's out there. When it comes to the Berkshires, the mountains block out the radar beam from picking up on whatever precipitation is falling and where. This will make it appear as a dry and clear spot on the radar when, in fact, rain is falling. The National Weather Service in Albany and Norton work together to determine if there are going to be any blind spots on the radar ahead of an impending 'low-hanging' storm to make sure folks are aware of it. Advertisement Have a question on a weather topic that you'd like to ask the Globe weather team? Let us know what's on your mind! To send in a question or comment, email You can also stay in touch with the weather team by to receive our that will arrive straight into your inbox bright and early each weekday morning. Ken Mahan can be reached at