Chase Field (Arizona)
Chase Field Ground Rule Particulars


Batted ball in flight strikes left of yellow line in left-center or right of yellow line in right-center: Home Run.

Batted ball strikes center field wall, girders or face of overhangs in center field on or between yellow lines and rebounds onto playing field: In Play.

Batted ball in flight strikes center field wall between yellow lines at a point above the shorter fence and continues over shorter fence: Home Run.

Batted ball in flight strikes above yellow line in batters’ eye and rebounds onto playing field: Home Run.

Batted ball in flight strikes the black pool gate beyond the right-center field fence: Home Run.

Batted ball in flight strikes higher fence of right field corner wall at a point above the lower fence and continues over the lower fence: Home Run.


Batted ball strikes roof over fair territory: In Play.
    • If caught by fielder, batter is out and runners advance at own risk.

Batted ball strikes roof over foul territory: Dead Ball.


Please refer to MLB Regulation 1-11 regarding the opening and closing of retractable roofs and/or wall panels and, where applicable, supplement with each individual ballpark’s guidelines for their retractable roof and/or wall panels.









• In Phoenix high temperatures can range from 70 degrees in March/April to highs of 115 in June/July.
• We begin to track the weather systems for each series approximately 3-4 days prior to each game.
• With average conditions (little to no wind and not very humid) during a typical evening game with first pitch of 6:40 pm, we can play with the roof open (while running air conditioning) with temperatures up to approximately 105 degrees.
• Temperatures higher than that will usually result in playing with the roof closed. (Note: in both scenarios, the wall panels would be closed to maximize the effects of the air conditioning system).

• During an average baseball season, we have what is called our “monsoon season” which typically runs from approximately July 7th to August 15th. This season can have windy, overcast days with chance of afternoon/evening showers, sometimes heavy.
• We again track our weather systems 3-4 days out and are usually at a point in the summer where the roof is closed during these months. The combination of high temperatures and high humidity, along with the chance of wind and rain, puts us in an “almost guaranteed” roof closed scenario.

• Size of crowd can play a large role in determining what position the roof and/or wall panels are in for a game.
• If we anticipate a smaller crowd in our upper deck seating area, it allows us a little more leeway in terms of possibly playing with the roof open during marginally higher temperatures. Not only will the majority of guests be cooled by the air conditioning, but we also have the ability to relocate our fans in the upper deck areas to “better cooled” sections in the same upper deck level, thereby ensuring a comfortable environment for all.

Game Start Time
• We have a lot of flexibility with our systems when dealing with scheduled evening games (6:40 pm or later).
• With start times like these, weather (temperature) becomes our main factor in determining whether the roof and/or wall panels will be open or closed.
• When we have scheduled games with start times ranging from 1:40 pm to approximately 3:00, this is where the multi-factor decisions come into play, i.e. weather (clear vs. cloudy skies), attendance, etc. We usually err on the side of caution when playing day games, primarily due to our north-facing ballpark which causes viewing issues for our fans down the first base line and right field, as they have to look directly back into the sun (assuming clear skies) while watching game action. (Note: for day games with comfortable outside temperatures, the wall panel system will usually be open. This combination allows fans to feel the outside element, despite roof being closed, and with minimal wind conditions, assists in air movement around the seating areas, all contributing to a more positive fan experience).

Shadows and Sightlines
• As noted in the section above, Chase Field is a true north-facing ballpark (as opposed to the traditional Northeast-facing parks) which presents “sun vs. shade” factors for our fans, players and television rights holders during day games.
• As a result of sun/shade studies we have conducted, we have concluded that day games can be played with the roof open (with acceptable temperatures) provided there is ample cloud cover to reduce/eliminate the sun situation down the first base line and in right field.
• These areas in particular, are of concern as players and fans are looking directly into the sunlight and thrown and batted balls can pose a hazard to those in the immediate area.
• In terms of our television rights holders, local network, Fox and ESPN have all done many games here and due to the changing shadow lines, would very much prefer to have their games broadcast with the roof closed.

Wind and Dust Storm Potential
• We live in a region of the country that lends itself to periodic wind and dust storm conditions, often times arriving into the downtown Phoenix area without much notice.
• As mentioned several times above, we continually monitor the National Weather Service and closely watch the weather radar screens on our computers to anticipate any irregular patterns.
• There may be times and conditions in which we may have to close the roof after starting the game with it open. (Note: we do not anticipate doing the reverse, i.e. starting with the roof closed and then later wanting to open it, due to weather conditions that may have already passed through during a game. However, as stated in Section B of the Bulletin, we reserve the right to discuss the possibility with the crew chief prior to the sixth inning).

Wind Speed Tolerances on Roof and Wall Panel System
• Wind speed tolerances for both systems are as follows:
• 15 mph maximum tolerance for wall panel systems and 30 mph maximum tolerance for the roof. Please note that the roof system has more of a window or range to move in, as its operation is based on being pulled in either direction (opening or closing) via its steel cables with really no slack so as to not enable the roof to “slide” on its own. So if wind speeds were consistently at 32 mph for example, the operating system would continue to move the roof, with a potential to temporarily stop or “fault” which would cause the system to be reset before continuing its movement.
• The wall panel system, on the other hand, has no window/range in terms of tolerance beyond the 15 mph limit. This is because, unlike the roof system, these wall panels are somewhat being “towed” via a horizontal shive system if you will, and in strong winds these panels have the ability to move faster than the “tow cables” are pulling it. And although there are large, spring-based, shock absorber-style “stops at both the fully opened and fully closed positions, strong winds could cause these panels to move somewhat independently of the cables with potential damage to not only the panels themselves, but the support structure around it. The best example in visualizing this would be a sailboat. Although the horizontal part of the mast is somewhat secured by rope, the sail still has the ability to move freely in changing winds. Although the rope prevents the sail from moving in a full 360 degree rotation, it does not prevent the sail from any wild motions that would cause tension on those ropes. In the case of our wall panels, any variation from the cables doing their job could cause considerable damage, and therefore following the tolerance limits are mandatory.

Universal Ground Rules:

The Commissioner’s Office has issued the following Universal Ground Rules for use in all Major League ballparks this season. Ground Rules pertaining to individual parks are posted separately in those parks.