One of the more consistent findings in climate science is that temperatures are not rising evenly through the day. Night-time temperatures are increasing faster than daytime temperatures. This pattern has been observed globally for decades and is well supported by both measurements and climate models.

The latest South African Weather Service Seasonal Climate Watch (April to August 2026) offers a clear, local example of how this shows up in practice.

What the current forecast shows

The SAWS outlook indicates that both minimum and maximum temperatures are expected to be above normal across most of the country during the coming months.

When you look more closely at the maps in the report, a difference emerges.

The minimum temperature forecasts show a strong and consistent signal. Almost the entire country is shaded in higher probabilities of above-normal conditions across all three overlapping seasons.

The maximum temperature forecasts tell a slightly different story. In the early part of the period, especially April to June, the signal is weaker and more uneven. It becomes stronger later in winter, but still shows more regional variation than the minimum temperatures.

These maps are probabilistic, so they show likelihood rather than exact temperature increases. Even so, the contrast between minimum and maximum temperatures is clear enough to notice.

What long-term observations show

This pattern is not new. It has been measured in observational datasets around the world.

Studies have consistently found that minimum temperatures have increased faster than maximum temperatures. One widely cited analysis found minimum temperatures rising at about 0.20 °C per decade compared with about 0.14 °C per decade for maximum temperatures.

As a result, the difference between daytime highs and night-time lows has been narrowing. This is referred to as a decrease in the diurnal temperature range.

More recent work continues to confirm this trend.

Why nights are warming faster

The explanation comes down to how the Earth loses heat.

During the day, the surface is heated by incoming solar radiation. At night, it cools by releasing heat back into the atmosphere and out to space. Greenhouse gases interfere with this cooling process by absorbing and re-emitting outgoing radiation.

The World Meteorological Organization describes this as an energy imbalance in the climate system, where more heat is retained than lost .

Because night-time cooling depends entirely on this loss of heat, it is more strongly affected. The result is that nights warm more readily than days.

Cloud cover, moisture, and local conditions can influence how this plays out regionally, but the overall effect is robust.

How this applies to South Africa

South Africa follows the same general pattern, although the strength of the signal varies by region.

Interior areas tend to show a clearer difference between minimum and maximum temperature trends. Coastal regions are more moderated by the ocean. Seasonal factors also matter, especially in winter when cloud and frontal systems affect daytime temperatures.

The current SAWS forecast fits into this broader picture. The stronger and more uniform signal in minimum temperatures, alongside a weaker early-season signal in maximum temperatures, is consistent with what has been observed over time.

What this means in practice

Warmer nights change how heat is experienced.

When temperatures stay elevated overnight, there is less opportunity for cooling. This can increase stress on people, crops, and ecosystems. It also affects energy demand and water use in ways that are different from daytime warming alone.

These impacts are not always as visible as extreme daytime heat, but they are just as important.

A careful reading of the latest forecast

It is worth keeping in mind what the seasonal outlook can and cannot tell us.

The maps show probabilities, not exact temperature changes. A stronger signal for minimum temperatures does not necessarily mean that the absolute increase in degrees will be larger than for maximum temperatures in every location.

What the forecast does show is where the confidence lies. In this case, there is stronger and more consistent confidence in above-normal minimum temperatures.

Closing thought

The idea that nights are warming faster than days can sound like a small detail, but it is a well-established feature of a warming climate. It appears in global datasets, in regional studies, and now in seasonal forecasts.

The latest outlook from SAWS reflects that same pattern. It is another reminder that climate change is not only about hotter afternoons. It is also about warmer nights that are becoming harder to cool down from.