According to sources close to the former Prime Minister, Ms Truss had been informed by the security services that the Kremlin leader might explode a weapon in the air above the Black Sea, which would show the West what he was capable of without triggering a full-scale nuclear war.
As with the Chernobyl accident in 1986, the radiation could pose a threat to Europe if it blew in this direction.
As a result, colleagues say Ms Truss became fixated with the weather forecast in the final days of her premiership.
The intelligence officials warned her that Putin might ‘go nuclear’ after Ukranian forces blew up the road bridge connecting Russia and Crimea, something the Kremlin leader had said would ‘cross a red line’ and prompt ‘judgment day’.
He also warned in a televised speech that if Western forces endangered the ‘integrity’ of Russian territory then ‘we will certainly use all the means at our disposal’, adding: ‘This is not a bluff.’
One source explained: “Liz was obsessed with the prevailing wind, watching the forecasts to see if she needed to trigger a Protect and Survive plan.”
Protect and Survive was a public information campaign on civil defence between 1974 and 1980 which advised the public on how to protect themselves during a nuclear attack. It detailed the warning signs when an attack was imminent and advised on what to do immediately after an attack, describing the effects of nuclear fall-out and how to plan for survival.
The source added: “Liz was terrified that news about her phone being hacked would come out because it looked almost symbolic of national weakness. Then, as her government was collapsing, she had to worry about nuclear clouds as well.
“We found her watching the weather forecasts with unusual interest.”
Radiation-detecting equipment is scattered across Europe as an early-warning system in the event of an accident or the deliberate use of a nuclear weapon, while cloud-mapping experts share information between countries about radiation direction.
Miss Truss resigned as Prime Minister earlier this month after a turbulent 45 days in office.