Balkans See Wide Day-Night Swings as Rain Targets Greece

Temperatures across the Balkans swung sharply between day and night last week, meteorologists Ed Walton and James Parrish reported for MetDesk in The Guardian, as a region of high pressure gave way to a low-pressure system now tracking toward Greece and set to bring heavy rain to the Aegean Sea by midweek.

What caused the Balkans' wide temperature swings?

An area of high pressure sat over the Balkans for much of last week, the forecasters reported. High pressure typically brings prolonged sunshine during daylight hours, pushing afternoon temperatures up. But the same clear skies that let the sun warm the ground during the day also let heat escape rapidly into the atmosphere after dark, with no cloud cover to trap it. The result, known as a wide diurnal range, is large separation between the day's high and the following night's low.

How extreme were the swings in Montenegro?

In Kosanica, a mountainous area of Montenegro, the average October maximum temperature is 15C (59F) and the average minimum is 4C, Walton and Parrish reported, a typical diurnal range of around 11C. On October 4 and 5, however, the gap between the daytime high and the overnight low reached 30C — more than double the seasonal average for the location, according to the Guardian report. The forecasters did not specify the exact high and low readings recorded on those dates, only the size of the swing between them.

Where is the heavy rain heading in Greece?

Elsewhere across Europe, high pressure is expected to build over the north and west of the continent over the coming week, the report said, pushing a separate area of low pressure southward toward the Mediterranean. That system will deepen as it crosses the Adriatic and Ionian seas before moving into the Aegean Sea by the middle of the week, according to the forecast. Greece is expected to see spells of heavy rain and strong winds as the low-pressure system passes overhead.

How much rain is forecast, and where will it fall?

Forecast models cited by Walton and Parrish point to widespread rainfall totals of 50 to 150mm across Greece, with the highest accumulations expected near the island of Skiathos. By the end of the week, the system is expected to continue moving eastward, bringing showers to parts of Crete — an island that was hit by severe flooding the week before, when storms swept cars and trees into the sea, according to the report. The forecasters did not provide rainfall totals or damage estimates for that earlier Crete flooding event, only the description of what the storms swept away.

Timeline of the pattern

• October 4–5: High pressure over the Balkans produces a diurnal temperature swing of 30C in Kosanica, Montenegro, more than double the seasonal average.
• Preceding week (before October 12): Severe flooding hits Crete, with storms sweeping cars and trees into the sea.
• Coming days: High pressure builds over northern and western Europe, pushing a low-pressure system south toward the Mediterranean.
• Midweek: The low deepens over the Adriatic and Ionian seas before moving into the Aegean, bringing heavy rain and strong winds to Greece, with 50–150mm forecast and the heaviest totals near Skiathos.
• End of week: The system tracks further east, bringing additional showers to Crete.

Is Hurricane Simon connected to this weather pattern?

The Guardian report also noted a separate system far from Europe: Hurricane Simon, a category 4 storm, moving close to Mexico's Pacific coast near Jalisco state. The forecasters described it as the 21st named storm of the Pacific season, with 11 reaching hurricane strength. At the time the report was filed, Simon had a central pressure of 933mb and maximum sustained winds of nearly 150mph (241km/h), the report said. Walton and Parrish noted that the storm is expected to weaken rapidly if its core moves onshore, since landfall would cut it off from the warm ocean waters sustaining its intensity. The report treated Simon and the Balkan-to-Aegean pattern as distinct, unconnected weather systems occurring at the same time in different parts of the world.

No additional data on soil saturation, flood warnings, or storm damage in Greece was included in the source report, and this article does not extend beyond what Walton and Parrish described for MetDesk.