Amman is veiled in rain. Water streams through the streets of the downtown area. Once we escape the city limits, the slate grey sky is clear and the road is dry.
During the downhill, roller-coaster ride to the plain, we see fields of bright green grass cropped short by herds of fat tailed sheep, hamlets where long, black woollen bedouin tents stand beside neat bungalows, an army camp surrounded by barbed wire, and a helicopter hovering in the sky near the turning to the air force base at Mafraq, where US forces are said to be training Jordanians on Patriot anti-missile equipment.
At Azrak we hurry by the castle built by the Romans in the third century and renovated in the 13th by the Ayoubid dynasty, founded by Saladin, the knight from Takrit, Saddam Hussein's hometown.
T.E. Lawrence stayed here in 1917 during the revolt which freed the Arabs from the Ottoman Turks and delivered them to Britain and France.
Beyond Azrak lies the bleak desert of black and cinnamon coloured basalt rocks and stones spread across flat pink sand.
The road from Azrak to the Iraqi border at Karama is as straight as a lance, flat as the blade of a sword.
Along it roar relays of yellow lorries carrying Iraqi crude oil for Jordan. All of Jordan's petrol, gas and heating oil comes this way, nearly a billion dollars worth, half free, half at half price. These are the last of the yellow lorries we will see for some time.
The border is marked by two arches, one for cars and the other for oil lorries. Normally there are long queues of tankers waiting for clearance.
Not today.
Only a dozen laze by the roadside, loath to begin the 500 km journey to Baghdad. A convoy of four CD-plate cars sweeps through from Iraq, possessions packed high in the back seats, the last diplomats to leave.
Camp B, for transients from third party countries, is 40 minutes' drive back along the road. Workmen are spreading tar and crushed limestone on the road and volunteers in white vests marked with the red crescent emblem are putting up the first family tent, designed to sleep five.
Three coachloads of volunteers from the Jordanian Red Crescent are trying to stretch canvas over the huge aluminium frames of four communal tents. But a freezing gale defeats them. Dr Muhammad Hadid, head of the Red Crescent, says: "We were hoping the elements would be gentler with us today." His 120 volunteers hugged themselves against the cold, waiting for instructions.
"We can put up 1,000 tents in eight hours," he remarks. "We are planning for 5,000 but can expand to 45,000." These refugees will be processed within 72 hours and sent home.
Camp A, another 8 km along, is for Iraqis. Here the Jordanian Hashimite Charitable Organisation and the UN High Commission for Refugees are partners in an effort to house an unpredictable number of desperate people. Street lights loom over roads which have not yet been made.
An engineer with his head swaddled in a scarf remarks: "We began work here last Wednesday and can finish tomorrow."
Ruweished, 60 km from the border, consists of a row of shops, tyre repair stalls and simple diners along the Iraq-bound side of the road.
Although most of the amenities are closed, Ruweished remains steeped in the heavy odours of petrol, charcoal smoke and grilled meat.
We find Douglas Osmond, UNHCR's field officer, at the settlement's premier restaurant.
"We have four staff and two drivers here at the moment and are expecting 15 Jordanian lawyers to deal with protection problems at the border," he says. "This is the most prepared camp site I've seen in my 14 years with UNHCR."
When I ask how long it will take to set up once the refugees arrive, he replies: "We can deal with 10,000 tonight."
Across the street a crowd has gathered round a Jordanian container lorry. Inside the chill metal container is an Iraqi family of 25 men, women and children.
A television team climbs in to film them as the children hold up a photo of their president and chant: "May God deliver Saddam Hussein."
They have had no water or food since they left home.
When the Jordanian police home in on the container, I rush back to the restaurant where Douglas is finishing lunch and inform him: "I think your first refugees have arrived and are in need of protection."