The Met Office said we can expect heavy rain and widespread strong winds on both Saturday and Sunday, although it is not expected to be as extreme as Storm Ciara last weekend, it said.
Amber and yellow weather warnings of strong winds and heavy rain have been issued for Sussex and other parts of the UK.
The Met Office said it possible that more than 100mm of rain could fall in some locations.
Paul Gundersen, chief meteorologist at the Met Office, said: “Another spell of very wet and windy weather is expected for Saturday.
“Although Storm Dennis is currently not expected to be as severe as Ciara, disruption is still likely.
“Our confidence in the forecast means we have been able to issue severe weather warnings well in advance, giving people time to prepare for potential impacts of the storm.
“With further warnings possible over the next few days people should keep up to date with the Met Office forecast using our website, app or by following us on social media.”
Over the weekend, wind gusts will widely exceed 50mph, the Met Office said, with gusts of over 60mph possible in coastal areas and exposed locations.
While these winds have the potential to bring impacts they are not as strong as the gusts we saw last weekend with Storm Ciara, it said, when a gust of 97mph was recorded on the Isle of Wight.
Heavy rain is expected and with already saturated ground, there is a risk of further flooding, the Met Office confirmed.
Travel disruption likely
Storm Dennis is expected to bring a range of impacts, including delays and cancellations to transport services, damage to power supplies and large coastal waves, the Met Office said.
Southern railway said high winds have the potential to damage overhead lines and tracks, for example through debris or lineside trees falling on to the railway.
It said Network Rail may need to put speed restrictions in place to keep passengers safe.
Southeastern Railway also said: “Amber and Yellow weather warnings of strong winds and heavy rain have been issued by the Met Office for large parts of the United Kingdom during the coming weekend.
“No changes to train services on Saturday or Sunday due to the forecast adverse weather have yet been announced, but further updates will be issued should anything change.
“However, if you’re planning on travelling this weekend, please make sure to check your journey before you travel through journey planners on the Southeastern website, On Track app, or National Rail Enquiries.”
Driving in storms, rain and strong wind
The Met Office said even moderate rain can reduce people’s ability to see and be seen when driving.
A spokesman said: “A good rule of thumb is ‘if it’s time for your wipers, it’s time to slow down’.”
The Met Office has issued the following advice:
• If heavy downpours are expected, avoid starting your journey until it clears.
• If you can, choose main roads, where you are less likely to be exposed to fallen branches and debris and flooding.
• Use dipped headlights if visibility is seriously reduced.
• Gusts of wind can unsettle vehicles – grip your steering wheel firmly with both hands. This is particularly important when planning to overtake.
• Keep an eye out for gaps between trees, buildings or bridges over a river or railway – these are some of the places you are more likely to be exposed to side winds. Ensure that you maintain enough room either side of your vehicle so you can account for it being blown sideways.
• Roads will be more slippery than usual in wet weather – be sure to give yourself more time to react when approaching a hazard. Increase your following gap to at least four seconds from the moving traffic in front.
• Keep your eyes peeled on the road at all times as spray from other vehicles can suddenly reduce your visibility. Remember it affects others too, so anticipate their actions and be prepared.
What to do when the road is flooded
• If the road is flooded, turn around and find another route. The number one cause of death during flooding is driving through flood water, so the safest advice is turn around, don’t drown.
• Although the water may seem shallow, just 12 inches (30cm) of moving water can float your car, potentially taking it to deeper water from which you may need rescuing.
• Flood water also contains hidden hazards which can damage your car, and just an egg-cupful of water sucked into your car’s engine will lead to severe damage.
• Never drive through flood water. Turn around.