A heat wave is affecting World Cup players and fans during the knockout round. The extreme temperatures are being felt in several host cities.

Forecasters have warned that the heat index values will be very high, exceeding 100 degrees when temperatures and humidity are combined. This is expected to pose a challenge to those participating in and attending the World Cup.

Further information on the heat wave and its impact on the World Cup can be found through KTXS, the local ABC affiliate in Abilene, Texas.