From the Rainlog.org data uploaded by members in my neighborhood, we've had almost exactly four inches of rain in the first six weeks of 2010. That's already more than half of what we received in all of 2009 (which was 7.14 inches).
Here's a photo in the wake of the storm that passed through January 22-23, 2010. This is 3/4 of a mile from where I live in north-central Tucson. Note the water flowing in the usually dry Rillito River, and the low level of snow in the Santa Catalina Mountains.
This is exciting stuff for us. One might first think about the spring wildflowers, but from Tucson southward and eastward, those sorts of plants that respond to winter rains with a flush of spring growth and bloom are not a significant part of our plant diversity. Such winter rains have been so unpredictable over the past few millennia in this region that they have been selected against. Instead, we have a large number of perennial plants (shrubs and trees, especially) that while amazingly well adapted to a dry, hot climate, simply cannot survive on just 7 inches of rain a year. Our average is 12 inches – with those summer rains being the most predictable. The rain we've received these past 6 weeks will go a long way to providing for these shrubs – hopbush, acacias, jojoba, kidneywood, babybonnets, sumac, etc. – many of which died, and many others which were just barely hanging on in this past year's drought.