WD40 works, if you're in a hurry, but might damage the seal, depending on the manufacture.
Petroleum Jelly (Vaseline) is pretty inert and will last for a long time and give some protection to the seal too, but it will also trap grit, meaning the paintwork may suffer over time.
Silicone mould release (for plastic moulding etc.) is dead slippery and chases water off, so that ought to work too. I find it as a spray lubricant for wood cutting tools such as router bits and saws (but don't use the PTFE stuff by mistake as that's rather bad for the environment). It is expensive though, and doesn't apply well by cloth.
My preference: clean the whole lot with warm soapy water. then apply petroleum jelly, well-rubbed-in, so there's the barest minimum on the surface. That ought to be a suitable compromise, and it does no harm.
SWMBO has done the same to the driver's door seal on the SAAB. I was very good and didn't remind her that I warned her at the beginning of the winter against yanking open frozen car doors. The affected seal runs from the bottom of the A pillar to the bottom of the C pillar, so will be dirt cheap. :-(
Fortunately the tear is only only about 15mm long and I have repaired it with Super Glue. The door seal on my very old Vauxhall Ashtray has similarly torn - but over a much longer length - perhaps 500mm. Super Glue has worked on that repair as well.
IIRC the UK-DIY newsgroup concluded that Silicone grease in spray form was effective at preventing the seals from freezing to the door. However, I find that a balance must be struck between freeze-proof seals and the cost of cleaning lube off SWMBO's office suits.
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