Drought conditions make hot weather even hotter

If it feels like this summer has been especially brutal, you're not imagining it. While the lack of rainfall is an obvious part of North Carolina's ongoing drought, there's another side effect that many people don't realize. Drought conditions can make hot weather even hotter.

On a typical summer day, the sun's energy doesn't just heat the air. When the soil is moist, a significant portion of that energy is used to evaporate water from the ground and vegetation. This process, known as evaporative cooling, acts like nature's air conditioner.

Evaporation requires a tremendous amount of energy. In fact, it takes roughly four times more energy to evaporate water than it does to raise the temperature of the same amount of land or air.

But during a drought, that cooling process begins to disappear.

With very little moisture left in the soil, far less of the sun's energy is spent on evaporation. Instead, more of that energy goes directly into heating the ground and in turn, the air just above it.

The result is noticeably hotter afternoons.

Water has an exceptionally high specific heat capacity, meaning it can absorb a great deal of energy before its temperature changes very much. Dry soil doesn't have the same ability.

Without moisture to absorb and redistribute heat, the landscape warms much more quickly. The hotter ground then transfers that heat to the surrounding air, allowing temperatures to climb even higher than they otherwise would.

It's one of the reasons droughts and heat waves often reinforce one another, creating a feedback loop that can make summer feel relentless.

History shows this isn't just theory.

During some of North Carolina's most significant droughts on record, average summer temperatures ended up running 1 to 3 degrees above normal. While that may not sound dramatic, even a small increase in average temperature can translate into many more days reaching the 90s or even triple digits.

This summer has followed that pattern. Temperatures are already running more than 3 degrees above average, and the ongoing drought is likely contributing to that extra heat.

There is at least one bit of good news.

Those same historic drought summers also tended to be slightly less humid than average. With less moisture available to evaporate, average dew points often run a degree or two lower than they otherwise would.

That doesn't eliminate the heat, but it can make the air feel just a little less oppressive on some days.

In a North Carolina summer, even a small break from the sticky humidity is welcome.

Drought doesn't just mean dry lawns, lower lake levels and stressed crops. It also changes the way the land interacts with the atmosphere.

With less moisture available for evaporation, more of the sun's energy is converted directly into heat. That helps push afternoon temperatures higher, adding another layer to an already hot summer.

Until widespread soaking rain returns, the drought is likely to continue doing more than drying out the landscape. It will also keep turning up the heat.