The Met Office has issued amber warnings of wind for much of the south west and a yellow warning stretching from southern Wales to the Thames Estuary as the storm sweeps in from the English Channel.
Imogen is threatening to fell trees, down power lines and wreak havoc with the morning commute, while high winds are expected to carry thundery downpours throughout the day that have the potential to cause problems into the evening rush hour.
Met Office forecaster Craig Snell said: “We have issued a broad yellow warning of wind that encompasses Cardiff, Bristol and into the Thames Estuary.
“There is an amber warning for wind mainly focussed on Devon and Cornwall but stretching into central England on Monday morning.
“This means people should be prepared for disruption to travel on roads, rail, bridges and ferries and we could see possible damage to structures and downed trees risk affecting power.
“The wind will be combined with some hefty showers with some thunder along the south coast.”
The warnings will be in place from 3am until 6pm on Monday, with gusts of 60-70mph expected widely.
Exposed areas on the south coast are on alert for gusts of 80mph with the potential to whip up “very large waves”, particularly in Cornwall and north Devon.
Forecasters said the morning rush hour will be “especially impacted” as Imogen tracks eastwards across an area south of the M4.