Heavy showers moved through the Fairbanks area late Tuesday evening and early Wednesday. The ASOS at airport recorded 0.98" between 10pm and 4am. So far no other site has reported quite that much; 0.62" at Keystone Ridge, 0.58" near College and University, 0.54" at UAF West Ridge, when generally less than 0.40" in the North Pole and Eielson AFB areas.
This amount of rain in such a short time of time (0.72" at the airport in just two hours) is quite unusual this late in the season, but there was a lot of moisture available. The afternooon RAOB Tuesday had 1.03" of precipitable water, and dew points got up to 56F early Tuesday evening, before the rain started in earnest.
The maximum 24 hour rainfall at the Airport of 1.05" Sept 7-8th appears to be the third highest September since 1930.