01:00 More Rain on the Way for the Northwest After a quick shot of storms, summer heat is set to return.

At a Glance Western wildfires are sending their smoke plumes across much of the United States.

This is causing unhealthy air quality in parts of the West, as well as unworldly sunrises and sunsets.

Dozens of wildfires are burning across the western United States, including at least 18 major fires in California alone , sending plumes of smoke across much of the country.

"Large wildfires from central and Northern California into northern British Columbia continue to burn and emit thick smoke, contributing to an expansive area of varying density smoke reaching from the Pacific coast eastward as far as Lake Superior and Hudson Bay and from the southwestern Northwest Territory to Guadalupe Island 150 miles offshore of Baja California ," NOAA wrote in a discussion Monday.

<img class="styles__noscript__2rw2y" src="https://dsx.weather.com/util/image/w/0807_current_fire_locations.jpg?v=at&w=485&h=273&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0" srcset="https://dsx.weather.com/util/image/w/0807_current_fire_locations.jpg?v=at&w=485&h=273&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0 400w, https://dsx.weather.com/util/image/w/0807_current_fire_locations.jpg?v=ap&w=980&h=551&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0 800w" > Each flame on the map represents an active large wildfire burning in the western United States as of Aug. 7, 2018.

NASA's Goddard Space Flight Center ran a computer-model simulation showing the aerosol index in the atmosphere from last Friday through Monday.

The various shades of teal and yellow in the maps below indicate higher levels of aerosols – smoke, in this case – in the atmosphere over a particular location.

<img class="styles__noscript__2rw2y" src="https://dsx.weather.com/util/image/w/omps_ai_us_2018_08_03-06.jpg?v=at&w=485&h=273&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0" srcset="https://dsx.weather.com/util/image/w/omps_ai_us_2018_08_03-06.jpg?v=at&w=485&h=273&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0 400w, https://dsx.weather.com/util/image/w/omps_ai_us_2018_08_03-06.jpg?v=ap&w=980&h=551&api=7db9fe61-7414-47b5-9871-e17d87b8b6a0 800w" > The various shades of teal and yellow indicate higher levels of aerosols – in this case, smoke – in the atmosphere over a particular location from Aug. 3-6, 2018. Yellow shadings show where aerosol concentrations are the highest. (NASA/Goddard Space Flight Center) (NASA/Goddard Space Flight Center)

The maps show that smoke was observed as far east as the southeastern U.S. coast and even parts of upstate New York and northern New England, though the highest concentrations of smoke were in Northern California, the Great Basin and portions of the northern Rockies.

Lick Observatory, east of San Jose, California, was engulfed in thick smoke Tuesday morning , the National Weather Service office in the Bay Area pointed out in a tweet.

The previous morning, skies were mostly sunny at the observatory , NWS-Bay Area also tweeted.

Satellite imagery showed a large swath of California blanketed with smoke Tuesday , which also led to air quality concerns in many areas.

The NWS has issued air quality alerts for portions of the West until further notice because of the ongoing wildfires in the region.

The simulation in the tweet below from the NWS office in Boise, Idaho, illustrates the total amount of smoke forecast to be in the atmosphere across the West through midday Wednesday .

The darker reds and purples indicate heavy amounts of smoke forecast over those respective areas.

The sunrise appeared rather unworldly in Seattle Monday morning, with the sky featuring a red glow as the sun was filtered out by wildfire smoke .

(MORE: Climate Change Is Making California's Wildfires Worse. So Are Humans. )

With hot, dry conditions returning to California and the Northwest this week, a critical fire danger will persist through at least Friday in parts of the region – bad news for the firefighters battling the ongoing wildfires.

(MORE: More Bad News for California, Northwest As Heat Builds and Fire Danger Continues )

Brian Donegan is a meteorologist at weather.com. Follow him on Facebook , Twitter and Instagram .