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When will we reach 100 degrees this summer?

While hot weather is in the forecast, we may not reach 100 degrees this season. However, the sunshine and heat will have an effect on our air quality.

COLORADO, USA — Temperatures are forecast to soar into the middle 90s by the end of the work week. The last time we were that hot was June 28 and 29. 

The above-average temperatures have a few of you asking if and when we'll reach 100 degrees this season. The answer may surprise you.

Credit: KUSA

We've been keeping weather records since 1872, and since then, Denver has only seen 89 days where the high soared to 100 degrees or above. 

That's less than 1% of the time. In fact, the percentage is so low, it counts for less than one day per year. 

We've reached 100 degrees at least once for the last three years, but in 2015, we didn't reach it at all. It's not a guarantee that we'll reach 100 every summer.

Even if we don't have those scorching hot temperatures, the hot weather and sunny skies is more likely to bring unhealthy levels of ground level ozone.

Unhealthy ozone levels

A hazy sky does not always mean ozone is high. There are a few ingredients that work together to bring us an unhealthy ozone level. 

Credit: KUSA

Ground level ozone occurs when warm temperatures and sunshine react with nitrogen oxide and volatile organic compounds (VOC's) from things like cars and places like power plants. 

The heat and sunshine are key in creating that chemical reaction that produces unhealthy ozone. So weather, including thunderstorms and wind gusts, will mix those ingredients out and reduce our ground ozone levels.

Unfortunately, wind and storms are not a part of the forecast for the end of the week. Already the Colorado Department of Public Health and Environment and the Regional Air Quality Council have issued an Ozone Action Day Alert for Thursday. Visibility is expected to be moderate and air quality unhealthy for sensitive groups, especially along the southern and western portions of the metro area.

It only takes a few simple steps...

The Regional Air Quality Council urges the community to do what we can to help reduce those levels. It only takes a few simple steps to get better air. Combining errands, taking public transit, and even packing a lunch can help reduce harmful emissions. 

Despite a disadvantage in location, the Rocky Mountains to the west and Palmer Divide to the south help trap unhealthy air over Denver. 

Our air quality has not been improving fast enough to meet the EPA's lowering standards for ozone.

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