Here's another online article about astrology and Hurricane Katrina:

Neptune Spawns Katrina

And here is an excerpt from that article:

"New Orleans, Katrina's point of attack on the U.S. coastline, is also the nexus of major oil and transportation systems. When this category five hurricane struck, not only did it create a huge regional mess, but the aftermath sent gas prices soaring across the country, and will likely lead to a significant recession beginning in a few months. As the most devastating natural disaster in U.S. history, the planetary indicators will be plainly visible in the U.S. horoscope.

All the key words describing this colossal tragedy – flooding, oil, victims, uncertainty and chaos – speak of Neptune. New Orleans itself, sitting below sea level, and the soul of the Blues, resonates with Neptune, the God of the Seas. In the Scorpio Rising chart (2:21 pm; July 4, 1776), transiting Neptune is right on the U.S. fourth house cusp, exactly opposite the Midheaven.

A fundamental principle in traditional astrology is that major events correspond to major transits to the angles. The four angles represent the points where spirit manifests in the material world. Without the connections to the angles, nothing of historic significance can happen. While slow-moving Neptune was passing over the U.S. fourth house cusp, along came Mars to trigger the hurricane. Mars and Neptune were exactly squaring each other when Katrina landed....

The Astrology of Hurricanes
Like other destructive hurricanes before it, Katrina arrived when all the outer planets were forming close aspects to each other. In Katrina's case, Jupiter and Neptune were trine, while the destructive duo Saturn and Pluto formed a tri-octile (135º aspect). Saturn was also opposite Chiron, which historically has been involved in these celestial currents.

Hurricane Andrew (August 24, 1992) was the previous holder of the most destructive, in terms of property damage. Andrew took place as Jupiter trined a Uranus-Neptune conjunction. Saturn and Chiron opposed each other, as well, with Pluto widely squaring both. Hurricane Camille (August 17, 1969) held the title before Andrew, and this one featured a Jupiter-Uranus conjunction opposite Chiron, and Saturn precisely tri-octile Pluto.

Naturally, the outer planet alignments influence the entire global weather system, but what fixates these stresses into the United States are the concurrent hits to the U.S. horoscope. Katrina is a perfect example, since transiting Neptune was (and is) right on the U.S. fourth house cusp. During Andrew's rampage, Chiron was right on the U.S. Midheaven (with Saturn opposite). Camille featured Saturn exactly conjunct the U.S. Descendant...."

Source: Michael (WolfStar) O'Reilly's NewsScope September 5, 2005