In this study, archived cloud-to-ground lightning data (source-BLM) from 2000 to 2007 was mapped on a 45 x 45 kilometer grid, and this was used to derive a climatology of thunderstorm occurrence over mainland Alaska (land areas not including the Aleutian Islands or Southeast (the Panhandle) Alaska). The lightning season is characterized primarily by diurnally driven thunderstorms that occur between late May and September, although isolated strikes are possible starting in late April and through early October. Most of the storms occur between 21 UTC and 09 UTC (1 pm to 1 am ADT), initiating at the warmest time of the day and weakening past midnight as the sun dips briefly below the horizon.

Nearly all parts of the state experience varying amounts of lightning. The most favored area of thunderstorm formation is an east-west oriented belt in the interior of the state between the Alaska Range to the south and the Brooks Range to the north. The area of highest lightning density with over 3000 strikes per 45 km gridbox is located in the east-central part of the mainland. The regions that recorded less than 25 strikes per 45 km gridbox are an area of high terrain in the extreme southeastern part of the mainland, and the Arctic Ocean influenced zone above 70° N latitude.

A vast majority of the lightning activity occurs in late June to early July when surface temperatures in the interior routinely exceed 20° C. Even during the peak of the season, most of the lightning occurs on just a limited number of days of the roughly four week period. These two to five day lightning outbreaks contribute a sizeable percentage toward the seasonal strike total.