>>> THE NEW STARTS NOW. >>> IS A FIRST ALERT WEATHER TODAY, ALL OF THIS SMOKE AND HAZE IN THE SKIES CAN BE DANGEROUS TO OUR HEALTH. SMOKE IS COMING IN, AND IT COULD HARM PEOPLE WITH HEALTH CONDITIONS. >> DENVER IS THE 16th WORST CITY FOR AIR QUALITY IN THE WORLD, ACCORDING TO THE AIR QUALITY INDEX. WE ARE LOOKING INTO THE IMPACT OF THE SMOKE WITH YOUR FIRST ALERT METEOROLOGIST, DAVE AGUILERA, TRACKING WHEN WE MIGHT CLEAR THINGS UP. ANOTHER HEAT WAVE IS MOVING OUR WAY. YOUR NORTHERN COLORADO REPORTER, DILLON THOMAS, IS LIVE TONIGHT. RESEARCHERS SAY, THERE ARE TWO MAJOR THREATS TO THE AIR QUALITY RIGHT NOW. >> Reporter: OF COURSE, RIGHT NOW, WE HAVE TO DEAL WITH THE ARIZONA WHICH IS ATTRIBUTABLE TO THINGS LIKE LAWNMOWERS AND VEHICLES. BUT QUITE LITERALLY, WE ARE SEEING SMOKE FROM FIRES AS FAR AWAY AS CANADA, WE CAN DO OUR PART TO CUT DOWN ON EMISSIONS FROM THINGS LIKE VEHICLES. BUT THE SMOKE IS LARGELY OUT OF OUR CONTROL. IF IT FEELS LIKE WE ARE SEEING MORE HAZY DAYS FROM THE SMOKE, WELL, IT IS BECAUSE WE ARE. >> CLIMATE CHANGE IS DRIVING THE INCREASES IN FIRES. >> Reporter: FEW THINGS MAKE THAT MORE OBVIOUS THAN THE AIR QUALITY IN RECENT DAYS. THE MAJESTIC MOUNTAINS OF COLORADO, CURTAINED BY SMOKE. THE VIEW OF THE DENVER SKYLINE, USUALLY VISIBLE FROM HUNDREDS OF MILES AWAY, BUT THE VIEWS ARE THE LEAST OF THE CONCERNS FOR MOST. CHERYL IS A PROFESSOR WITH THE DEPARTMENT OF RADIOLOGICAL HEALTH, SAYING THAT HEALTHCARE SPIKE DURING DAYS LIKE THIS. >> WE SEE INCREASES IN EMERGENCY ROOM VISITS AND PHYSICIAN VISITS. >> Reporter: SOME MAY JUST EXPERIENCE ITCHY EYES, FOR OTHERS IT IS LIFE-THREATENING. >> WE ARE WORRIED ABOUT PEOPLE WITH ASTHMA. >> Reporter: PREGNANT WOMEN ARE AT RISK AS WELL. >> SMOKE CAN PASS THROUGH THE PLACENTAL BARRIER AND IMPACT THE FETUS. >> Reporter: YOU CAN SEE THE RED AND ORANGE POOR QUALITY WARNINGS STRETCHING FROM THE NORTHWEST AND CANADA THROUGH COLORADO. >> THINK ABOUT FIRES, WILDFIRES, THIS IS AN EMERGENCY. COLORADANS ARE ALSO GETTING USED TO BEING AFFECTED BY FIRES , THERE ARE SEVERAL IN THE MOUNTAIN WEST, AND UP IN CANADA. >> Reporter: WHETHER THIS WILL BE BACK? >> IT DEPENDS ON METEOROLOGY AND TOPOGRAPHY, THE WAY THE WINDS CHANGE, THAT WILL IMPACT COMMUNITIES. >> Reporter: WE KNOW THAT THIS CAN IMPACT PEOPLE WITH EXISTING HEALTH ISSUES, THE DATA IS NOT REALLY THERE FOR HOW IT IMPACTS OVERALL HEALTHY INDIVIDUALS AS THE STATISTICS USUALLY COME FROM PEOPLE WHO WERE COMING INTO THE HOSPITAL FOR TREATMENT AND OTHERWISE HEALTHY PEOPLE TEND TO DO THAT LESS OFTEN. EXPERTS SUGGEST THAT PEOPLE STAY INSIDE, CONSIDER USING YOUR AIR CONDITIONER, THEY USUALLY HAVE FILTERS IN THEM. ON THAT NOTE, MAKE SURE TO SWAP YOUR FILTERS AS WELL. DILLON THOMAS, COVERING COLORADO FIRST. >>> DYLAN WANTS TO HEAR ABOUT WHAT IS IMPACTING