1. Introduction
With two outs in the bottom of the ninth inning in a 24 August 1919 game against the Philadelphia Athletics, Cleveland Indians pitcher Ray Caldwell was knocked unconscious after a lightning flash at the ballpark (Osborne 2017). Although Ray Caldwell would quickly recover and finish the game, the event illustrates the hazard that lightning poses to outdoor events.
Lightning is a high-current electrical discharge that occurs between the cloud and the ground, within a cloud, between multiple clouds, or between the cloud and the air. The overall lightning discharge is known as either an in-cloud (IC) flash or a cloud-to-ground (CG) flash that is made up of individual components called pulses for IC flashes and strokes for CG flashes. These components are detected by lightning detection networks. Interested readers can learn more in Uman (2001).
Globally, lightning kills as many as 24 000 and injures as many as 240 000 people annually (Holle 2016). In the United States, annual lightning fatalities averaged 30 yr−1 between 2006 and 2019 (Jensenius 2021). Two of the U.S. fatalities were amateur baseball players, a 12-yr-old Virginia boy in 2009 and a 26-yr-old South Carolina man in 2011, who were killed during games (NWS 2021a). Holle (2005) identified in the NOAA Storm Data publication (dating to 1959) and in media reports 28 baseball and softball casualty cases that resulted in 13 deaths and 96 injuries. Because it is primarily an outdoor leisure activity, baseball puts players and other team members, officiating and stadium crews, vendors, and spectators at risk of lightning injury or death. Holle (2005) recommends lightning safety education and warning procedures that account for players, officials, and spectators.
Major League Baseball (MLB) is a professional baseball league with 30 teams in the United States and Canada. The 30 teams are distributed across geographically diverse regions with large differences in annual lightning density (Fig. 1). Teams play 162-game seasons that begin in late March or early April and end in late September or early October. Although beyond the scope of this paper, spring training, playoff, and minor league games, many of which are played outdoors, add additional opportunities for lightning-related incidents at professional baseball games. Between 2001 and 2019, there were an average of 73 million fan visits to Major League Baseball games per year (ESPN 2021). Seven MLB ballparks during the period of study had either fixed or retractable roofs. Table 1 provides more details of the individual ballparks in this study.
Map showing locations of MLB stadiums (black dots) overlaid on NLDN average total lightning density from 2015 to 2019.
Citation: Weather, Climate, and Society 14, 2; 10.1175/WCAS-D-21-0099.1
Details of the MLB stadiums used in this study. The Atlanta Braves moved from Turner Field to Truist Park after the 2016 season.
The baseball season coincides with the peak of lightning season in the United States. More than two million CG flashes are detected per month from April through September in the National Lightning Detection Network (NLDN) domain (Holle et al. 2016). Although the overall probability of lightning striking a particular point is low (Krider 2003), exposure to lightning in a large outdoor venue creates a potential hazard for players, crew, and spectators.
Challenges with lightning safety at large outdoor venues are well-documented (e.g., Gratz and Noble 2006; Woodrum and Franklin 2012). The American Meteorological Society (AMS 2018a, 2018b), National College Athletics Association (NCAA 2014), and National Athletics Trainers’ Association (NATA; Walsh et al. 2013) have all issued statements or created policies about lightning and weather safety at venues and sporting events. It can take substantial time to move large groups of people to safety, so preparations for lightning must take place before lightning arrives within the safety threshold. The National Weather Service (NWS) developed a Lightning Safety Toolkit (LST; Woodrum and Franklin 2012; https://www.weather.gov/safety/lightning-toolkits) for outdoor venues, with additional toolkits now available for communities, golf courses, and lifeguards. The LST complements the StormReady (NWS 2021b) program that supports the greater Weather-Ready Nation (WRN; NWS 2019) initiative.
Previous studies (e.g., Gratz and Noble 2006; Holle and Flanagan 2018) have looked at lightning around football stadiums, but no studies have examined lightning around baseball stadiums. To understand the magnitude of the lightning hazard at MLB games, lightning data surrounding each MLB ballpark during more than 9700 baseball games between 2016 and 2019 were analyzed. Statistics for each ballpark and a discussion of lightning safety for MLB games follow.
2. Data and methods
a. Baseball game information
Game information including ballpark, date, start time, and length of game were collected from the Baseball Reference website (https://www.baseball-reference.com/). Each MLB ballpark was geolocated to obtain its latitude and longitude, which would be used as the center point for the lightning data search. Date and time bounds for the lightning data search were set to be 1 h before the game start time and 1 h after the game end time. Occurrence and duration of weather or other delays were not available. The extra hours before and after each game were added to account for people being in and around the ballpark before and after each game, respectively.
b. Lightning data
IC pulse and CG stroke lightning data within 12.8 km (about 8 mi) of each baseball game between 2016 and 2019 were downloaded as shapefiles from the Vaisala, Inc., NLDN archive through the Lightning Exporter tool (https://lightning-exporter.vaisala.io). The 12.8-km radius is set as the initial radius to suspend outdoor events in the LST. Lightning data shapefiles were opened in QGIS (https://www.qgis.org) for display and data analysis.
NLDN is a network of more than 100 lightning detection sensors distributed throughout the contiguous United States, spaced approximately 300–350 km apart (Zhu et al. 2020). In 2016, the NLDN processor was updated to remove the +15-kA boundary of small positive events classified as IC pulses (Murphy et al. 2021). NLDN has high CG stroke detection efficiency (Zhu et al. 2016) and detects approximately 50%–60% of IC flashes (Murphy and Nag 2015). The CG location accuracy is better than 100 m (Zhu et al. 2020). This study includes all lightning detected by NLDN, regardless of IC or CG classification, as the inclusion of IC lightning can improve lightning safety metrics (Schultz et al. 2017).
3. Results
Between 2016 and 2019, 717 baseball games had lightning detected within 12.8 km of the ballpark (Table 2). Of 30 ballparks, 27 had lightning games, defined as a game with lightning within 12.8 km, with only Dodger Stadium, Oakland Coliseum, and Petco Park lightning free; 272 of the lightning games occurred at stadiums with either fixed or retractable roofs. During the 717 lightning games, 49 700 CG strokes and 124 891 IC pulses were detected by NLDN.
Number of lightning games and lightning discharges within 12.8 km for each MLB stadium during the study period. Asterisks indicate stadiums with roofs.
Lightning games occurred in all months in which regular season games are played except October (Fig. 2). There is an increase in lightning games as the MLB season moves into the peak of lightning activity across the United States in the summer months, with a maximum of 176 lightning games in August, the month with the second-most CG lightning over the NLDN domain (Holle et al. 2016).
The number of MLB lightning games in each month for the period of study. August has the most lightning games, with 176 between 2016 and 2019.
Citation: Weather, Climate, and Society 14, 2; 10.1175/WCAS-D-21-0099.1
Table 3 shows the total lightning (IC pulse and CG stroke) counts and the lightning density for three different regions for MLB lightning games: within 0.15 km, between 0.15 and 1.6 km, and between 1.60 and 12.8 km. Within 0.15 km approximates the ballpark itself, between 0.15 and 1.60 km is immediately outside the ballpark, and from 1.60 to 12.8 km is the area surrounding the ballpark. Only 31 total lightning discharges were detected at the stadium, just 0.02% of all lightning events, but the lightning density per lightning game at the ballpark is about 30% higher than the surrounding areas (0.61 discharges per square kilometer per lightning game vs 0.47 discharges per square kilometer per lightning game). Eleven of the discharges detected at the ballpark were classified as CG strokes. It is important to understand why the lightning density is higher at the ballpark than in surrounding locations. Future work should seek to evaluate the difference in density values.
Lightning counts and lightning density for MLB lightning games.
Games played in Miami and Saint Petersburg, Florida, were most likely to have lightning nearby, with 80 and 78 lightning games, respectively. The distribution of lightning games across the league is not uniform, however. There is a strong linear fit in the relationship between a ballpark’s annual lightning density and its number of lightning games (Fig. 3a) and between the annual lightning density and the amount of lightning detected within 12.8 km (Fig. 3b), with R2 (correlation squared) values of 0.686 and 0.7678, respectively.
Scatterplots comparing (a) the number of lightning games at MLB stadiums (y axis) with average annual lightning density at the stadium (x axis) and (b) the number of lightning discharges detected within 12.8 km of games at MLB stadiums (y axis) with the average annual lightning density at the stadium (x axis).
Citation: Weather, Climate, and Society 14, 2; 10.1175/WCAS-D-21-0099.1
4. Discussion
Between 2016 and 2019, 9717 regular season MLB games were played, with approximately 1 lightning game for every 14 games played. There was a wide range in number of lightning games for individual ballparks, from 0 to 80, which is nearly one-quarter of a team’s home games. Although eight currently used ballparks have retractable or fixed roofs, lightning is a significant risk to all 30 teams, as well as fans, stadium support crew, and other people in and around the ballpark.
The official MLB rulebook has two rules that specifically mention lightning safety [Rules 4.03(e) and 4.04(a); MLB 2019]. These rules were included in the official MLB rulebook for the first time in 2019. The text in both rules state, “Nothing in this Rule is intended to affect a Club’s ability to suspend or resume any game pursuant to a policy governing severe weather, significant weather threats, and lightning safety that has been filed with the league office prior to the championship season.” It is unclear how many teams have filed plans with the league office or are aware of the updated rules. Without a policy in place, any weather-related delays or suspensions during a game fall to the umpire-in-chief, who has nine duties listed in the official MLB rulebook [Rule 8.03(a); MLB 2019].
Numerous high-profile lightning events have occurred at MLB games in recent years. As an example, on 23 July 2020, MLB started the season after a lengthy delay because of the coronavirus disease 2019 (COVID-19) pandemic. The New York Yankees and Washington Nationals played at Nationals Park in Washington, D.C. Around 0055 UTC 24 July 2020 (2055 23 July 2020 local time), the umpire-in-chief delayed the game when rain reached the stadium. In the 34 min prior to the delay of the game, 2993 IC pulses and CG strokes were detected by NLDN within 12.8 km of Nationals Park (Fig. 4). Lightning was visible on camera during the television broadcast, and CG strokes were as close as 2 km from the ballpark before the game was delayed.
Map showing the locations of the 2993 lightning discharges detected by NLDN within 12.8 km of Nationals Park between 0021 and 0055 UTC 23 Jul 2020.
Citation: Weather, Climate, and Society 14, 2; 10.1175/WCAS-D-21-0099.1
Despite challenges, lightning is recognized as a threat to baseball games, and efforts to improve lightning safety have been undertaken. As of June 2021, the MLB Commissioner’s Office had been recognized for completing the LST and seven MLB teams had been recognized as StormReady Supporters (NWS 2021b; Table 1). A StormReady Supporter “is an organization . . . actively engaged in weather safety and preparedness” (NWS 2021b). In 2004, then–Minnesota Twins star player Torii Hunter participated in an NWS lightning safety campaign (Fig. 5). Other efforts have included teams installing purported lightning prevention devices, although “neither data nor theory supports claims that ‘lightning elimination’ and ‘early streamer emission’ techniques are superior to conventional lightning protection systems” (Uman and Rakov 2002).
NWS lightning safety poster from 2004 featuring then–Minnesota Twins center fielder Torii Hunter.
Citation: Weather, Climate, and Society 14, 2; 10.1175/WCAS-D-21-0099.1
Long term gains to lightning safety at MLB games can be achieved using existing frameworks and statements, like those from the AMS, NWS LST, and NATA Position Statement on Lightning Safety for Athletics and Recreation. Under rules 4.03(e) and 4.04(a) of the MLB rulebook, lightning safety plans filed with the league office can take the responsibility of lightning delays from the umpire-in-chief and give it to individual teams. Designated weather watchers or on-site meteorologists can then monitor for approaching lightning and other weather hazards and implement safety procedures before lightning is at an unsafe distance from the stadium.
5. Conclusions
Lightning poses a significant safety risk to MLB games, with nearly 175 000 lightning discharges detected within 12.8 km of 717 regular season games between 2016 and 2019. Nearby lightning has been visible at MLB ballparks during televised games and on team social media profiles.
Although the MLB rulebook allows for teams to file lightning safety policies with the league that would give them responsibility of lightning delays, it is unclear whether any teams have filed such policies. Lightning safety at MLB games could be significantly increased if teams filed lightning safety policies, using the NWS LST and NATA Position Statement on Lightning Safety for Athletics and Recreation as guides to create their policies.
Acknowledgments.
The author thanks his fellow members on the National Lightning Safety Council for discussions of lightning safety topics, including that of lightning safety at sporting events. The author also thanks the reviewers for helping to improve the paper.
Data availability statement.
Data in this study are from the Vaisala, Inc., National Lightning Detection Network. Information about obtaining NLDN data for academic studies can be requested from the author.
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