AUSTIN -

As summer temperatures soar in Texas, city and state health officials are urging people to be aware of the signs of heat illness and to take precautions to protect themselves from heat exhaustion and heat stroke.

The City of Houston has activated its Heat Emergency Plan now that the region is under an excessive heat advisory.

Houston activates the plan when the heat index, a computation of air temperature and humidity, reaches 108 on two consecutive days.

High-risk groups such as adults age 55 and older, children under the age of five and people with chronic illness are urged to stay inside air-conditioned buildings between 1 p.m. and 5 p.m., the hottest part of the day.

Anyone without access to air-conditioning can seek shelter during business hours at city multi-service centers, libraries or recreation centers. Houstonians may call 311 and ask for the nearest open city facility. A list of the facilities can be found here.

METRO can also provide transportation to the nearest cooling site. Arrangements for transportation can be made by calling 311.

If air conditioning is not available, the Texas Department of State Health Services suggests opening windows, pulling down shades to keep out direct sunlight and using fans to cool rooms.

Experts said the best defense against heat-related illness is prevention. Stay cool, drink plenty of fluids, wear cool clothing and limit strenuous outdoor activities.

Health officials offered the following tips to prevent heat-related illnesses:

•Increase water consumption. Drink lots of liquids even before getting thirsty, but avoid those with caffeine, alcohol or large amounts of sugar because these can actually result in the loss of body fluid.

•Conduct outdoor work or exercise in the early morning or evening when it is cooler. Outdoor workers should drink plenty of water or electrolyte-replacement beverages and take frequent breaks in the shade or in an air-conditioned facility. Those unaccustomed to working or exercising in a hot environment need to start slowly and gradually increase heat exposure over several weeks.

•Check on the elderly. Take the initiative to visit seniors to look for signs of heat related illnesses. It takes the elderly nearly twice the time of younger people to return to core body temperature after exposure to extreme temperatures. A phone call to the frail elderly is not sufficient to determine the condition of the senior or the home.

•Wear light-colored, loose fitting clothing that permits the evaporation of perspiration.

•Do not leave children, senior citizens or pets unattended in a vehicle.

•A wide-brimmed hat helps prevent sunburn as well as heat-related illness. Sunscreen also protects from the sun’s harmful rays and reduces the risk of sunburn.

•If the house is not air-conditioned, seek accommodations in air-conditioned facilities during the heat of the day: malls, movie theaters, libraries, etc.

•Take frequent cool baths or showers if your home is not air-conditioned.

•Electric fans should only be used in conjunction with an air conditioner. A fan can't change the temperature of a room; it can only accelerate air movement, and will accelerate the body's overheating.

•Stay alert to heat advisories. The National Weather Service declares a Heat Emergency when the heat index, a computation of the air temperature and humidity, reaches 108 degrees on two or more consecutive days. A heat index of 108 is a potential health threat for all people and is particularly dangerous for high-risk groups.

City officials said during an excessive heat advisory, utility companies are prohibited from disconnecting service due to lack of payment.

>>Click here for a list of cooling centers.