Highland Thunderstorms Push Flash Floods Across 13 Arab Countries

Saudi Arabia’s weather service kept red alerts on Jazan through 8 p.m. on Friday, October 2, for heavy rain, hail and flash floods. Arab Weather’s August 11 map of thunderstorms across 13 Arab countries still matches the same afternoon highland pattern, and floodwater was already moving through Jazan wadis by mid-afternoon.

The National Center for Meteorology also called moderate to heavy thunderstorms on Asir, Al-Baha, Makkah and Madinah, with lighter storms farther north and dust-raising winds toward Riyadh. NCM said the wider thunderstorm chance would last from Friday, October 2, through Tuesday, October 6.

Rain on the Ridges Runs Straight Into the Wadis

Sinan Khalaf, a forecaster at Arab Weather, wrote on August 11 that moisture at several heights, plus strong heating of the ground, would keep building thunderclouds in the afternoon and evening. The 13-country thunderstorm forecast put the heaviest chances on mountains, with hail, lightning, downdrafts and sudden runoff in low ground and valleys.

Rainfall chances are particularly concentrated over mountainous and highland areas, where local rainfall may be heavy and accompanied by thunder, lightning, hail, and downdrafts, which may lead to flash floods in some low-lying areas and valleys.

Sinan Khalaf, weather forecaster, Arab Weather, August 11, 2026

That split, rain on the crest and water in the channel, is the part that keeps turning up in official warnings. It is also what Friday’s videos from Jazan showed: hail in Al-Aridah, and brown water already running in Wadi Razan, east of the city, while the red alert was still in force.

A Red Alert From Noon Until 8 p.m.

NCM’s Friday forecast for five regions kept “moderate to heavy thunderstorms that lead to torrential rains” on Jazan, Asir, Al-Baha, Makkah and Madinah, with hail and a chance of fog on those highlands and on the Eastern Province coast. Light to moderate thunderstorms were listed for Tabuk, Al-Jawf, Hail, Qassim and the northern and eastern borders.

A separate early-warning notice, alert 85464, set a Jazan red alert until 8 p.m. on Friday, October 2, from noon, for heavy rain. The listed effects were active winds, a loss of horizontal visibility, hail, torrential rain and thunder strikes. The governorates named on that notice were Abu Arish, Ahad Al Masarihah, Al Fateha, At Tuwal, Damad, Sabya and Samtah.

FRIDAY TEMPERATURES AND STORM SIGNALS

Abha’s 28 C high sat 8 C below Jazan’s 36 C, the usual gap between the escarpment towns and the Tihamah plain. Southern Red Sea winds were forecast at 10 to 30 km/h, rising to 50 km/h with thunderclouds, and wave heights there climbing above 2 metres in those cells.

WHAT WE KNOW

• The Friday core: NCM kept moderate to heavy thunderstorms on Jazan, Asir, Al-Baha, Makkah and Madinah, with hail.
• The red alert: Heavy rain for seven Jazan governorates from noon to 8 p.m. on October 2.
• On the ground: Hail and running wadis were filmed in Al-Aridah and Wadi Razan that afternoon.

WHAT IS UNCONFIRMED

• Asir’s alert tier: Asir is in the Friday rain forecast; the fetched red-alert file names Jazan, not Asir.
• How long cells last: Local downpours can start and finish in a short window even when the daily outlook stays wet.

In early September, NCM had already told the public that the severe end of this pattern includes heavy rainfall exceeding 50 millimetres per hour and gusts exceeding 60 km/h, with flash floods, hail and high waves along the coast. That intensity is what turns a ridge shower into a wall of water in a steep wadi.

Afternoon Storms Build on Three Highland Belts

The 13-country list reads like one weather system. It is three belts that happen to fire in the same season, each tied to mountains and to heat after midday, not to a single front crossing from Oman to Morocco.

THREE BELTS ON THE MAP

• The Asir-Yemen-Hajar chain: Daily thunderclouds on southwestern Saudi highlands, Yemen’s western mountains, Oman’s Hajar range and, more weakly, the UAE’s eastern highlands.
• The Levant and northern Egypt: Local afternoon and evening showers on coastal hills in Syria and Lebanon, with thinner chances in northern Palestine and northern Egypt.
• The Maghreb, Libya and Sudan: Atlas and upland storms in Morocco, Algeria and Tunisia, limited cells in northern Libya, and broader rain in southern Sudan fed by tropical moisture from the south.

Oman’s weather service had flagged Hajar thunderstorms and downdrafts in early September, including a medium-impact window from 1 p.m. on the mountains. Yemen’s National Center of Meteorology and Early Warning was still, on October 2, expecting thunder-rain of mixed strength on Taiz, Ibb, Raymah, Al Mahwit and Hajjah, with more scattered cells on Amran, Al Dhale’a, Dhamar and Saada, plus parts of the Tihama and the western coast. The UAE’s weather service, in late September, did not treat the Saudi and Oman storms as a system that would move in directly, and kept the interior closer to fair or partly cloudy.

Why the Asir Escarpment Keeps Building Thunderclouds

Southwestern Saudi Arabia sits where moist air from the Red Sea and, in the warm months, from the southwest monsoon is forced up a mountain wall that rises more than 3,000 metres. The steep western face gets the lift; the Tihamah plain below gets the runoff. Towns on the ridge stay cooler, as Friday’s 28 C in Abha and 26 C in Al-Baha showed beside Jazan’s 36 C, and the same slope that makes the highlands liveable makes the wadis fast.

Researchers mapping Wadi Hail in Asir, a basin of 5148.70 square kilometres that drains toward the Red Sea, built a flash flood model for Wadi Hail using satellite rain and a distributed hydrology run. They found 43.8% of the basin in the high flood-risk class. A test storm of only 1 millimetre of rain over 8 hours still produced a peak of 8.8 cubic metres a second at the main outlet, because the network is dense, the ground is hard, and the relief is sharp.

Jazan’s floods have the same geometry: short, steep basins that fill quickly, then empty toward the coastal plain. That is why a red alert that names inland governorates is also a warning for roads and settlements that never see the cloud that started the water.

Valley Beds Are the Place the Warnings Name

Saudi Arabia’s General Directorate of Civil Defense has been repeating one instruction through this season: stay in a safe place, stay away from valleys and flood-prone ground, and do not swim in the water. On September 18 it tied that advice to thunderstorms then expected through the following Tuesday, with moderate to heavy rain and hail on Taif, Maysan, Adham and Al-Ardiyat in Makkah region, and on Jazan, Asir and Al-Baha. On October 2 it named Madinah, Jazan, Al-Baha and Makkah again.

Yemen’s weather service used the same geography. On September 26 it warned drivers off valley beds and flood channels, and flagged poor visibility on mountain roads in cloud and fog. On October 2 it told people to keep out of wadi bottoms and flood paths, to stay off high ground and metal structures in thunderstorms, and to watch for fog on highland roads.

The advice is old because the failure is old. Video from Jazan in August showed a vehicle that entered a running wadi and was swept. Replies to that clip treated it as a seasonal habit, Civil Defense talking and someone still trying the crossing. Friday’s Al-Aridah and Wadi Razan clips sat in the same groove: the water is in the channel while the cloud is still on the ridge.

HOW THE HIGHLAND SEASON HAS RUN

1. August 11, 2026: Arab Weather publishes the 13-country highland thunderstorm outlook, pointing to afternoon cells and valley floods.
2. August 12, 2026: Video from Jazan shows a car taken by floodwater after it enters a wadi.
3. September 3, 2026: NCM warns that heavy bursts can exceed 50 millimetres an hour, with gusts above 60 km/h, flash floods, hail and high coastal waves.
4. September 18, 2026: Civil Defense tells the public to stay out of valleys and flood-prone ground as rain continues on Makkah, Jazan, Asir and Al-Baha.
5. September 26, 2026: Yemen’s weather service warns against standing in valley beds and flood channels.
6. October 2, 2026: NCM holds the Jazan red alert from noon to 8 p.m.; floodwater runs in Al-Aridah and Wadi Razan.

Fifty-two days separate the August 11 bulletin from Friday’s alerts. The country list was a seasonal envelope. The wadi problem did not take a break.

Where the 13-Country Forecast Puts the Rain

Khalaf’s August 11 rundown, and later Arab Weather updates in the same vein, never promised equal rain from Muscat to Marrakesh. They named highlands, then attached a local hazard to each range.

WHERE THE RAIN WAS AIMED

Sudan’s rain is the odd one out: less a mountain afternoon storm than a northward push of tropical moisture. Algeria’s extra hazard is dust, as downdrafts lift sand and cut visibility. Makkah sits on the Saudi list because cells sometimes drift off the Asir-Al-Baha chain toward Taif and neighbouring governorates, which is why Civil Defense has kept naming the region even when the heaviest alerts sit farther south.

Lightning Already Clusters on These Same Highlands

Arab Weather’s own climatology, written in 2023, put the Arab world’s densest lightning over southern Sudan, the highlands of southwestern Saudi Arabia, and western Yemen, the same summer thundercloud belt, with the equatorial rain band pushed north. Next in that ranking came southern Mauritania and the Aures between Algeria and Tunisia. The desert strip between Egypt and Libya sat at the bottom.

Globally the same note cited about 3 million lightning flashes a day, about 44 a second, with more of the cloud-to-ground strikes over land than over sea. That background is why a “13-country” headline keeps returning each warm season: the map is a climatology wearing a forecast’s clothes. The actionable piece is narrower. Watch the ridge in the afternoon. Treat the wadi as live until well after the thunder stops.

On Friday afternoon in Jazan, that sequence was already on camera. Hail in Al-Aridah. Water in Wadi Razan. The red alert still running until 8 p.m.