Why Are Days So Hot and Nights So Cool Right Now in Indiana? Here's the Science Behind It

Photo byWTHR

If you’ve been stepping outside lately in central Indiana, you’ve probably noticed a dramatic swing in temperatures—scorching 90°F days followed by cool nights dipping into the 50s. So, why does the weather feel so drastically different between day and night right now? The answer lies in a phenomenon known as radiational cooling.

The Dry Air Effect

Indiana is currently experiencing very dry conditions. The air’s low humidity means it can heat up and cool down quickly. During the day, with clear skies and the sun blazing, the lack of moisture allows temperatures to soar into the upper 80s and even 90°F. But as soon as the sun sets, the same dry air loses heat rapidly, allowing evening temperatures to plunge. This results in those brisk overnights we’ve been experiencing.

Additionally, the dry ground exacerbates this effect. Dry soil has a lower heat capacity than damp soil, meaning it absorbs and releases heat much more quickly. This combination of factors leads to the wide temperature range we’re feeling—warm days, followed by notably cooler nights.

What to Expect This Week

According to forecasts, these conditions will continue, keeping temperatures above average. Monday and Tuesday will see sunny skies with highs in the upper 80s. A slight chance of rain appears on Wednesday as remnants of a tropical system move through the region, though the dry air in place will make it difficult for the moisture to take hold. Expect cooler temperatures briefly on Wednesday, with highs in the low 80s.

By Thursday, the skies clear again, and temperatures will rise back into the mid-80s. As we approach the weekend, expect temperatures to climb once more into the upper 80s, continuing the trend of hot, dry days and cooler nights.

What is Radiational Cooling?

Radiational cooling refers to the process by which the Earth loses heat during the night. After sunset, without the sun's energy to warm the ground, the heat accumulated during the day escapes into the atmosphere. This process is particularly efficient in clear, dry conditions—exactly what central Indiana is experiencing. The result? Chilly overnight lows, even after sweltering afternoons.

As the week progresses, don’t be surprised to feel the heat rise again during the day. Just be sure to pack a light jacket if you’re heading out in the evening—radiational cooling will be in full effect.