Portland, Ore., isn't known for sunny weather. Yet when it rains this weekend, as it's expected to, the athletes competing at the IAAF World Indoor Championships won't feel a drop. 

Indoor track and field meets are relatively new in the world of athletic competition. Unofficially, the first was held in 1863, in London, England, in a grand hall on the grounds of Cremorne Pleasure Gardens, according to Spike magazine, the publishing arm of the International Association of Athletic Federations. There were four running events and the triple jump.

The IAAF held its first official international indoor meet in 1985, in Paris. They moved to Indianapolis, Ind., two years later and have been held every two years since.

But history isn't the only element that differentiates indoor and outdoor events, at least at the international level.

1. There are fewer indoor disciplines than outdoor ones.

At the highest level of IAAF competitions, outdoor track and field is made up of 28 events: 18 track and eight field, plus the combined events of decathlon (men) and heptathlon (women). Indoors, on the other hand, has just 15: eight track, five field, and the heptathlon (men) and pentathlon (women).  

2. The track is shorter indoors.

Indoors, the track is 200 metres — half its outdoor size. That means athletes have to run more corners and tighter turns indoors than they would outdoors; instead of making four corners to complete the 400, they must make eight. 

Because they're running at top speed, the corners of most indoor tracks are banked on an angle of between 10 and 15 degrees. The vertical transition between flat straights and banked bends is continuous and uniform to make it easier for athletes to pass easily from straights to bends.

3. Distances are mostly shorter indoors.

Indoors, the 100 metres becomes the 60 metres. The 400, 800 and 1,500 remain, but the 5,000 becomes the 3,000. The 200, 5,000 and 10,000 don't happen indoors at the world championship level; neither does the marathon or race walk. Oh, and there's no steeplechase, as there's no water jump. 

4. There are fewer throwing events.

Field events take place in the open oval formed by the track, called the infield. A smaller track means less space for field events, and shorter distances for throwing events.

Outdoors, you have javelin throw, hammer throw, discus throw and shot put. Indoors, it's shot put. 

And shot put has more security precautions, too. Outdoors, shot putters throw into a landing area enclosed by an arced board, painted white. Indoors, the landing area is enclosed at both ends with a barrier and protective netting to keep any other athlete or official from getting hit by a shot. 

Can you imagine the precautions it would take to secure the javelin area? Shudder.

5. Times are generally slower indoors.

In the 400, the men's outdoor record is 43.18; indoors, it's 44.57.

In the 800, the women's outdoor record is 1.53.28; indoors, it's 1:55.82.

Blame track size for this one. Although there are no weather factors to contend with (wind, sun in the eyes), running around more corners forces athletes to slow down more often — and that affects their times.

Want to learn more? Follow CBC Sports' exclusive live online streaming coverage at CBCSports.ca and via the CBC Sports app for iOS and Android devices, as well as additional coverage on CBC Sports' Road to the Olympic Games TV broadcasts.

For full streaming and broadcast details, click here.