The hottest three days of the summer are expected Tuesday through Thursday.The National Weather Service has issued an excessive heat warning for Columbia River Gorge and northern Willamette Valley, along with most Clark County communities. The warning takes effect at 2 p.m. Tuesday and will last until late Thursday night.Daytime high temperatures are forecasted between 98 and 103 degrees for the Portland-Vancouver area during the next three days. Tuesday’s high will peak near 100 degrees, but things will only get hotter from there.“It will be warmest in urban areas,” the weather service said.Heat and humidity may cause heat stress, especially with the limited relief at night.Precautions are encouraged, as forecasters issue the warning when a “prolonged period of dangerously hot temperatures” occur. Here’s what residents can do: Drink fluids. Stay in air-conditioned rooms, if possible. Stay out of the sun. Check on friends and neighbors. Reschedule strenuous activities to early morning or the evening. Wear lightweight and loose-fitting clothing. People should also know the signs of heat exhaustion and heat stroke. The former generally involves cool, moist skin with goosebumps, even when in the heat while the latter causes red, hot, dry skin. Read more about the differences between the two illnesses here.Heat stroke is an emergency, so call 911.