We are publishing regular cloud forecast updates leading up to the total solar eclipse on Aug. 21. Confidence is still fairly low, but confidence will get higher and our predictions more specific in the days leading up to the big event.
The eclipse is just one week away, and we are at the point where forecast models can start piecing together the general weather pattern for Aug. 21. However, not until about three to five days before the eclipse — or even later — will regional details start to come into focus. So we still must paint the cloudiness outlook with very broad strokes. Continue to take it with a grain of salt, and we would not recommend altering plans based on it.
Forecast confidence: Low
- South-central U.S. and eastern Midwest look best
- Tricky low clouds and storm chances in western Midwest
- Southeast battles scattered p.m. storms
- Smoke, fog, low clouds complicate Pacific Northwest
Forecast confidence: Low to medium
Corvallis, Ore. — Morning fog likely to burn off in time for good view
Madras, Ore. — Mostly clear but light smoke haze possible
Rexburg, Idaho — Widely scattered clouds but plenty of breaks likely
Casper, Wyo. — Partly cloudy, breaks possible
Forecast confidence: Very low
Grand Island, Neb. — Greatest risk area for mostly cloudy conditions
St. Joseph, Mo. — Partly cloudy, occasional interference a concern
St. Louis — Partly cloudy, some interference possible
Carbondale, Ill. — Scattered clouds, limited interference
Hopkinsville, Ky. — Scattered clouds, limited interference
Nashville — Scattered clouds, limited interference
Greenville, S.C. — Partly cloudy, occasional interference possible
Columbia, S.C. — Partly cloudy, occasional interference a notable concern
Charleston, S.C. — Partly cloudy, occasional interference possible
Average weather conditions for Aug. 21
The timing of the eclipse is ideal, at least for the West. It begins just after 10 a.m. local time on the West Coast, which is usually enough time to burn off the fog that often occurs there.
The intermountain areas sometimes see thunderstorms bubble up in the afternoons during this time of year. These are associated with the Southwest monsoon, a period of increased thunderstorms and rain during the late summer and early fall. But the eclipse passes through this region around noon, before most of the storms develop, so the storm risk should be low there.
Clouds often pop up along the rest of the path throughout the day simply because of warmth and moisture. Those two things combined lead to rising air, which creates clouds. So the cloud risk gets greater the farther east you go. On top of that, South Carolina will see totality the latest in the day — after 2:30 p.m.
NASA created the map below which shows how, on average, the best chance of clear skies on Aug. 21 focuses in western areas and the chance of cloud cover increases as you head east.
Additional cloud cover resources:
- National Weather Service eclipse forecast page
- NOAA GOES-16 satellite images
- Historical cloud cover information from NOAA
Jason Samenow contributed to this post.