Pollution spikes have become as much a part of 4th of July as fireworks. And there's no reason to think this year will differ. State air-quality officials forecast "yellow" pollution days today and Saturday. That means people with respiratory illnesses, the old and the young should take care not to overdo outdoor activities. And Utah's city dwellers can help limit air pollution by driving less and keeping their lawn and garden power equipment idle during the hot afternoon hours. It's too soon to tell how worrisome ozone and smoke pollution will be Sunday and Monday. Yet, if past years are a guide, the end of the holiday is also bound to have "moderate" air quality, too. "Anywhere there's fire- works, there will be pollution," said Cheryl Heying of the Utah Division of Air Quality. Pollution forecasts for Sunday and Monday have yet to be made. Generally, the hotter and more windless the weather, the more likely it is that ozone pollution builds. July is often a high ozone month in Utah. The National Weather Service expects it to be sunny all weekend. Daytime temperatures around Salt Lake City are predicted to be in the low 90s Friday and Saturday. Slightly cooler temperatures are expected for the rest of the holiday weekend. So far, there has been just one "moderate" air-quality day this year. - Judy Fahys