It's all because of another area of low pressure, which will hang around in some shape or form until Friday. There are plenty of isobars on the chart indicating brisk winds but there is a bit of a gap between weather systems which looks like it'll bring some drier weather in time for Saturday.
For the rest of this evening that band of persistent rain will continue eastwards, with a Met Office warning coinciding with rush hour. Frequent, heavy and blustery showers will follow across Devon, Cornwall and the Isles of Scilly overnight but there should be a drier spell further east. By morning though, the same band of rain will back track, bringing low cloud and some fog. There could be a bit of snow across the top of Dartmoor and Exmoor too. Temperatures will drop to around 3 Celsius.
Thursday will probably be the coldest day this week with plenty of cloud and further spells of rain throughout. After that cold start temperatures will struggle, reaching no higher than around 6 or 7 degrees across parts of Gloucestershire and Wiltshire. The Isles of Scilly could see double figures but the strong northerly winds will make it feel colder.
There will be a few more showers around on Friday, followed by a mostly dry day on Saturday. However, another area of low pressure looks like it'll arrive on Sunday bringing more wet weather.