Spaceweather.com has more on Comet McNaught and how you may be able to see it even during the day:
Observers around the world are reporting that Comet McNaught is now visible in broad daylight. The comet is very close to the sun, so it is tricky to find. If you want to try, here's how to do it: Go outside and stand in the shadow of a building so that the glare of the sun is blocked out. Make a fist and hold it at arm's length. The comet is about one fist-width east of the sun.This assumes, of course, we ever see the sky again around here.
This weekend is a special time for Comet McNaught because it is making its closest approach to the sun. Solar heat causes the comet to vaporize furiously and brighten to daytime visibility. McNaught is now the brightest comet in more than 40 years, and it may become the brightest in centuries.