Chicago Marathon officials upgraded the status of course conditions to "moderate" due to the warmer than average temperatures in the forecast for Sunday.

The "moderate," or yellow, level is the second lowest status, with "high" (red) and "extreme" (black) as the worst levels for runners.

The upgrade was prompted by the weather conditions for Sunday's race as temperatures are expected to soar into the 70s. Skies are also expected to be sunny, and a warm breeze is likely to sweep Chicago during the race.

The warm weather will have the greatest impact on runners who complete the marathon in 4.5 to six hours as the early morning temperatures will be much lower.

Marathon officials encourage runners to drink enough fluids, including sports drinks, to maintain their baseline body weight, but they warn runners not to over-hydrate.

Warmer temperatures require more energy and resources when running, so officials encourage participants to consider running at a slower pace to prevent overheating.

Dressing appropriately is also key in the warmer conditions. Runners should avoid cotton fabrics, long sleeves and long pants. Instead, they should wear lightweight, breathable fabrics that will keep them cool. Sunglasses and waterproof sunscreen are also essential to protect runners' skin and eyes.