Not being a very knowledgeable fan of baseball, I have always been puzzled by this. Why can’t the sport of baseball be played when it’s raining? Other outdoor sports, such as American football, lacrosse, and soccer all continue playing if it starts to rain. What is it about baseball that causes immediate postponement if a few drops of water start to fall? 
Baseball is hardly cancelled at the first sign of a few drops of water. Saturday night’s Yankees-Angels game was played in the rain the entire time because it was just a light drizzle.
The main reason is that it’s just tradition to not play in the rain. It’s a summer game. Another reason is that it becomes a bit more dangerous to play in the rain. The ball become harder to control when it’s wet, which is a bad thing when you’ve got guys throwing 95 mph within a foot or two of the batter. Plus, baseball in wet conditions is just bad and ugly to watch. No one wants to watch a game of baseball where the pitchers can’t get control, errors are being made, the runners are slow, etc. when it’s not raining and no one wants to see that kind of garbage being played when it is raining, either.
There’s just no good reason to play in a heavy rain except to satisfy a TV schedule.
I have seen videos of Japanese Major League games being played in quite hard rains where rain delays are apparently not usually permitted.
In addition to what has been said, do you really want your $15M pitcher breaking his leg when his lead foot slides off the mound? (Houston’s Oswalt had a bad slip last night on a dry mound.) Or someone get hurt sliding in the mud while running bases?
Soccer: Cleats on grass. No 100MPH “spitball”.
Football: Ditto plus lots of padding and helmets.
I lean towards safety first.
Baseball isn’t playable in very heavy rains because much of the game depends upon people being able to throw the baseball precisely. If it’s raining too hard, you can’t do that.
Also if the field gets so wet that there are puddles on the field, that will create unplayable conditions. The ball should be able to roll through the grass and dirt, not get stuck in mud.
A sport like football can be played in most rainy conditions because it’s not as hard to have a guy hold on to a ball and run through mud. That said, it’s still not artistic to watch.
Fun though! Nothing is more fun than watching a football game in the mud!
Except for a game in the snow.
Being struck by a baseball can seriously injure or even kill a person. If it’s raining hard enough to seriously impede vision, it’s simply common sense to stop playing.
This time of year, you’ll see games played that probably wouldn’t be in the regular season, due to TV demands. I don’t think the game the other night would have gone on had it been July.
While Japanese games may be played during heavy rains once they’ve already started, they also cancel games at the slightest hint of rain during the day.
The Japanese leagues build makeup days into the schedule and they play every game on the schedule at the end of the year to make them up even if the pennant has already been decided and it’s two tailenders playing each other.
One thing I’ve noticed from visiting Japan is that for a country where it rains a lot, the Japanese have an extreme phobia about getting wet. I never use an umbrella when I travel there. I just bring a waterproof jacket and put the hood up. I feel out of place.
Then again, I’m a 6’5" white guy walking around Japan too.
The players’ safety is a real and important consideration. But it mostly is that baseball players and fans are smart enough to come in out of the rain. 
In addition to the above, consider how slick grass can get when it’s raining. It makes things particularly risky for the outfielders, who have a lot of wet ground to cove.
[hijack]Ha. Funny you should say that. Just a few days ago I had a Japanese guy say exactly that to me (as he led us into the Metro corridors for a circuitous alternate underground route to our restaurant, rather than braving a 150 yard walk through the lightest of drizzles) “Japanese people are very afraid of rain.” They are also very into umbrellas, umbrella stands, umbrella drying gadgets, and wrappers for umbrellas. I asked why this was so. The reply: Because it’s so humid in Tokyo that once you get wet, you’ll never dry. I have a variant on this theory. Yes, it’s damn humid and sticky in the Summer. But in most of the rest of the world, you’d deal with this by going into a well air-conditioned office. Not Japan, where the CoolBiz program has office thermostats set at 82 degrees (no joke) and where I swear the air conditioning that does exist rehumidifies, rather than dehumidifying, the stuffy air.[/hijack]
True. But how is any different for sports that are played in the rain, e.g. soccer and football?
Maybe because a running outfielder is often looking stright up into the air instead of where he’s going?
As a comparison, cricket is a game that usually stops during the rain. Like baseball with the pitcher? you have a bowler who has to be able to control the ball and that is almost impossible when it’s wet.
I assume pitchers put a spin on the ball to control its flight, as do bowlers. Although spin bowlers only bowl at about 50mph, fast bowlers can bowl at nearly 100mph. If the ball was to slip out of the hand at that speed it could fly anywhere.
Soccer is played in some pretty bad conditions, but if the field (pitch) is really soggy or frozen, they’ll call the game. Frozen is a bigger problem. Frozen fields and soccer are not a good mix. It hurts a lot.
Costa Rica clinched its World Cup spot with a 3-0 win over the US at home in San Jose in a driving rain storm. As long as the field holds up reasonably well, you can slog through it. Although the game is played with the feet, the ball is travelling in the air a lot. I like matches played in snow where they use an orange ball. I’ve also seen balls deflate in midair because of the cold.
I think in any sport the big problem is puddles forming on the field. Big puddles will cause just about any sport to be postponed until they can be taken care of. Golf is played in the rain unless the rain is so extensive that the greens have standing water or there is lightning.
They will stop American football games because of lightning in the immediate vicinity.
Maybe you meant Friday night’s game?
http://mlb.mlb.com/NASApp/mlb/news/article.jsp?ymd=20051008&content_id=1242772&vkey=news_nyy&fext=.jsp&c_id=nyy
Give it a try and you will understand why. Trying to play baseball in heavy rain is miserable. Excessive water changes everything about the game and negates many of the learned and necessary skills. The danger of a poorly controlled fastball between pitcher and batter is obvious but a more subtle example is that a fielder needs to see the ball come off the bat so that he can play it properly. An outfielder may be 300 feet from where the ball is batted. Do you really want to watch a game where the fielders can’t react properly to a batted ball? Do you want to be an infielder taking a throw from the outfield and not know where it’s coming from. The game can quickly be reduced to a farce.
Football, on the other hand, doesn’t change that much in the rain. Yes, the passing game becomes more problematic but the game can be played pretty much as designed. Once the players get used to being wet they hardly notice the weather. The fans are more affected by the weather than the players. If heavy fog or snow sets in whereby a passed or kicked ball cannot be seen the game will be suspended or delayed.
Lightning is also another reason why baseball isn’t played in the rain. Baseball is played during the spring and summer and, in North America, rainfall during this time of year often comes in the form of thunderstorms. The risks posed by lightning strikes are greater during baseball season than it is during football season since that sport’s mostly played during the fall when rain is less likely to be accompanied by lightning.
A better question is, why do they play football games in miserable weather?
Answer: There are far fewer games in a college or pro football season, and making up a cancelled game is problematic. Teams can only play once a week, and squeezing a makeup game into an off week during a season is very difficult.
Baseball, on the other hand, has a very long season, and teams usually play several series against each other each year. So, if a Yankees-Orioles game in April gets rained out, there are probably goiung to be numerous opportunities to make up for that lost game over the course of the season. So, why WOULD you make the players and fans suffer through a deluge if it’s not necessary?
In cricket or baseball, the fielding team will have an enormous advantage in moderate to heavy rain given the different visibility and frictional conditions of the ball and bat, and there is no guarantee that the conditions will be the same for their innings (in cricket, the call of who gets to bat first is already an extremely important factor, even with no rain play).
In football etc., both teams labour under the same conditions at the same time, and no specific advantage is gained. So, really, it’s just to increase the skill:luck ratio required to win.
Nonsense. They can always play a doubleheader. 
I think the main concern with cricket in the rain is that the batsman can’t see the ball which makes it pretty dangerous. Generally when it’s raining the bowling team are quite happy to stay out, knowing that it’s just getting harder for the batting side. It is still a valid comparison with baseball.