Yellow weather warnings, which will remain in place until midnight on Friday, have been issued for the rest of Wales and large parts of northern England and southern Scotland.
The main impacts for the United Kingdom will be from heavy rain across some western areas on Friday and Saturday, with yellow Met Office weather warnings for wind and rain now in place for Friday and Saturday.
A zone of heavy rain associated with an intense weather system affecting western parts of the United Kingdom will become slow moving for a time, bringing prolonged rainfall and the potential for surface water flooding.
Throughout Friday and Saturday, areas covered by the warnings could see between 50-100 mm on Friday and 50-80 mm on Saturday.
The Met Office has warned heavy rainfall could present a risk to life. Further strong winds may bring down leaves and branches, increasing the likelihood of flooding due to blocked drains or culverts. Winds will also be an issue with gusts over 50mph.
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Director Stephen Stewart said: "Even though power cuts are rare, during times of heavy rain and flooding they become more likely. Road users should also be aware of the risk of their vehicles aquaplaning on standing water".
A video from the Met Office has shown the impact that Storm Callum will have on the United Kingdom as a whole and when it will head east.
Natural Resources Wales' (NRW) have said they are sending out their emergency response teams to prepare for the storm, checking that flood defences are in good working order, clearing gulleys and ditches, and installing temporary defences.
Rain will then hit Edinburgh on Friday afternoon, becoming increasingly heavier into the evening.
SEPA said that high tides are expected to affect the area Argyll and Bute and Ayrshire and Arran and Skye and Lochaber in particular, due to "a storm surge and large waves" associated with the storm.