Given its location in the middle of the Outback, it should come as no surprise that Alice Springs doesn't exactly have a "wet" season. Rainfall varies from year to year, but overall the climate is dry and arid most of the time. If there has been a considerable amount of rain during the winter, the wildflowers and plant life will spring up all over during August through October.
As for temperatures, it can get as high as 48°C and in the winter can drop as low as -7°C. The best time to visit this area is in April and thereabouts - you'll miss out on the incredibly hot days of the summer, as well as still be far enough away from the cold season. As many travelers use Alice Springs as a jumping off point for visiting Uluru, this time of year is also the best time to visit the big rock and National Park since during the summer months, it can be downright unbearable during the day to hike or walk around the park.