However, since 1999, 5 of the violent tornadoes have occurred during the month of May. Note that 18 of the 27 April tornadoes were F2 or greater, and that 5 of the 12 F4/F5 tornadoes on record occurred in April. Strong and violent tornadoes tend to occur slightly earlier, with April the peak month. About two thirds of all tornadoes in OKC have struck during those three months. May is the peak month for all tornadoes, followed closely by April and June ( Figure 2). Weak events (F0 and F1) before 1950 had no assigned F scale in any of the available sources, and thus have been assigned an estimated rating based on the available data. Notes are included in the narrative of an event if differences were found in the F-scale ratings among the available sources. Events listed as F2 in the SPC database, but not appearing in Grazulis 1990, are listed here as F1. Since Grazulis lists only events of F2 intensity or greater, any event not found in his listing has been given a rating of either F0 or F1. The extensive research conducted by Grazulis (1990) suggests his ratings to be the most reliable, and they have been used when the ratings differed among the available sources. However, there were occasional differences, especially with F-scale ratings. In general the multiple sources were in good agreement. Many of the events were found in more than one data source. A dollar estimate of damage (if available and not adjusted for inflation) and the data sources used for each tornado entry are included at the end of each narrative. A narrative describing what is known about the event follows the other data. The cities of Edmond, El Reno, and Norman are not included, which means that tornadoes striking within their city limits are not listed unless they also affected the immediate OKC area.Д®ach of the 171 tornado listings (see the OKC Tornado Table Tab) contains the date and time of initial touchdown (note that all times are CST) or a total time range (if available), maximum tornado path width and length, maximum F Scale or EF Scale rating (see the Appendix Tab for descriptions of the F Scale and EF Scale), number of people killed and injured (from the entire event), counties included in the path, and a brief description of the path. In addition to OKC, the following jurisdictions are included: Bethany, Choctaw, Crutcho, Del City, Forest Park, Jones, Midwest City, Moore, Mustang, Nichols Hills, Nicoma Park, Valley Brook, the Village, Warr Acres, Witcher, and Yukon ( Figure 1). All recorded tornado events occurring wholly or partly within this area are included in the list. The resulting area ( Figure 1, hereafter called the 'immediate OKC area') includes roughly 600 square miles. In order to establish a consistent area, it was decided to include the present OKC limits and all other surrounding cities and towns that are contained largely or wholly within those limits. Peripheral townships have emerged as well over the years, some of which are now wholly surrounded by OKC city land. OKC covers a large area today, but the city limits have changed over the years such that some areas that are now part of OKC were not always within the city limits. After 1950, records were cross-checked using Storm Data and the severe weather database compiled at the Storm Prediction Center (SPC).ДЄ second obstacle arose in determining exactly where the OKC city limits are - or were. Thus there are no records on weak tornadoes prior to 1950 (unless they happened to make it into the WSFO listing), and so the true number of tornadoes probably is much higher than the total arrived at herein. The compilation by Grazulis includes all tornadoes of F2 intensity or greater, and all killer tornadoes, from 1880 through 1989. The only readily- available data source prior to 1950, other than the local records on station at WSFO OKC, was Grazulis (1990). One was the lack of reliable sources for events that occurred before 1950. This turned out to be a formidable task, for several reasons. In 1991, a project was initiated to revise the list by adding recent tornadoes (since 1978), validating existing entries, and searching for any others that might have been overlooked. Sometime later, record keeping ceased for some reason and the existing list was relegated to a binder that was lost among the growing masses of other records that accumulated at the office. That list included 43 tornadoes as of 1978. The source of the number most likely was a local listing, kept on station at the National Weather Service Forecast Office (WSFO OKC). In the 1960s and 1970s, news and magazine articles sometimes quoted the number of times OKC has been struck by tornadoes that number typically was in the 30s or lower 40s, depending on the year of publication. Oklahoma City (OKC), by virtue of its large areal extent and location near the heart of 'tornado alley,' has earned a reputation over the years as one of the more tornado-prone cities in the United States.

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