Blocking pattern brings ‘second summer’
October kicked off this week, but it doesn’t feel much like spooky season just yet. Temperatures remain unseasonably warm across the region, continuing the hot, dry stretch that closed out September. Highs have been running 10 to 15 degrees above average, while overnight lows have stayed mild, making it feel more like late summer than early fall.
This stretch of warm, dry weather isn't just by chance. It's being driven by a large-scale weather phenomenon known as atmospheric blocking.
A blocking pattern occurs when two low-pressure systems, or troughs, set up on either side of a high-pressure ridge. This formation causes the atmosphere to become locked in place, limiting the movement of weather systems and resulting in days—or even weeks—of consistent weather.
Over the past week, a strong ridge of high pressure has been centered over the central United States. This high-pressure system causes air to sink, which compresses and warms the atmosphere. That sinking air also suppresses cloud development and traps heat closer to the surface, which is why skies have remained mostly clear and temperatures have stayed high.
When there’s little vertical movement in the atmosphere, heat builds up and rain chances decrease significantly.
Thankfully, this ridge is gradually shifting eastward as we head into the weekend. As it moves out of the region, the blocking pattern will begin to break down, allowing more typical autumn weather systems to return.
While the first week of October may have felt more like summer’s encore, changes are on the horizon. Cooler days, rain chances, and more fall-like conditions will finally be making their way back into the forecast.
