Contrary to what may be assumed, fallen meteorites are not hot; the heat caused by atmospheric friction abrades the outer layers, stripping away the heated portions, leaving the remaining portion as cold as they were while still in space. A free-falling meteorite spends less than thirty seconds in the atmosphere, which is not enough to heat it through. Touching a freshly-fallen meteor is more likely to cause frostbite than a burn.
The meteor trails clearly show that a number of them are following distinctly different trajectories. If, as it was stated, they all originated from the same comet or asteroid, all meteor trails would be parallel. Michelle mentions that the radiant is in Cassiopeia; this means that all the meteors would appear to be coming from that point in the sky traveling directly towards the observer, not following transverse paths.
The pattern of meteor strikes is shown as crossing the USA from west to east, but the earth rotates in the opposite direction.
It's stated that assistance is need from the Russians as "our satellites won't be in position, but theirs will". However, satellites don't remain in just one place, unless they are in geosynchronous orbit, when they'd be able to contact the ICBMs. In any case, there are sufficient US communications satellites around the Earth for several of them to be in a suitable position to contact the ICBMs. In addition, the Deep Space tracking Network makes use of major radio-telescopes around the Earth, of which at least one would always be in a position to contact something in space.
The initial launch footage of what is supposed to be an American ICBM is actually that of a Russian Soyuz launcher.
Just before the bridge collapses its deck is undulating wildly in a wave-form yet the vehicles on the deck don't move at all. In reality they would be thrown off or at least thrown about.
The city of San Francisco is equipped with an emergency civil defence siren system. During a disaster, this system would be activated, yet it was never heard during the events of the film.
Despite the fact that the film was set in San Francisco, at one point in the background, you can see a Vancouver bus drive past.
When Brad is being driven to the hospital by the two reporters, a sign on an automobile collision shop says 'I.C.B.C.' I.C.B.C. is a provincial Crown corporation found in the Canadian province of British Columbia, and does not have any jurisdiction in San Francisco, California, U.S.A.