Upper Geyser Basin
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Upper Geyser Basin clear sky chart from 2005-11-06 to 2024-01-15.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	5% 9% 5% 8% 7% 4 5% 5% 5% 7% 39%	74811
	Night	4 8% 5% 9% 7% 4 5% 5% 6% 7% 40%	74963
Transparency	Day	44% 8% 13% 19% 13% 4	74514
	Night	44% 8% 14% 19% 12% 4	74781
Seeing	Day	13% 20% 31% 23% 11% 2	14345
	Night	11% 15% 29% 31% 14% 2	24098

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	3 12% 9% 13% 10% 5% 6% 5% 7% 7% 22%	1333
	11th to 20th	Day	2 12% 7% 12% 11% 4 6% 4 5% 6% 31%	1569
	21st to end	Day	2 14% 8% 16% 10% 5% 5% 4 5% 5% 26%	1782
February	1st to 10th	Day	3 14% 8% 14% 11% 5% 6% 5% 5% 7% 22%	1620
	11th to 20th	Day	2 14% 8% 16% 11% 5% 5% 4 5% 6% 24%	1575
	21st to end	Day	2 11% 11% 21% 13% 5% 5% 4 4 4 19%	1412
March	1st to 10th	Day	2 14% 6% 15% 10% 4 7% 5% 5% 5% 25%	1933
	11th to 20th	Day	3 13% 7% 10% 7% 4 5% 6% 5% 8% 30%	1980
	21st to end	Day	5% 18% 9% 15% 8% 4 5% 5% 5% 6% 20%	2178
April	1st to 10th	Day	6% 17% 8% 11% 8% 5% 5% 5% 5% 6% 26%	2078
	11th to 20th	Day	6% 14% 6% 11% 9% 5% 5% 5% 5% 6% 28%	2276
	21st to end	Day	8% 16% 5% 9% 6% 4 5% 6% 5% 7% 29%	2340
May	1st to 10th	Day	9% 12% 4 9% 8% 3 6% 5% 6% 7% 32%	2340
	11th to 20th	Day	8% 7% 4 8% 7% 4 7% 6% 7% 11% 32%	2406
	21st to end	Day	13% 11% 4 8% 8% 5% 6% 6% 6% 8% 25%	2724
June	1st to 10th	Day	12% 8% 3 5% 6% 4 6% 6% 7% 9% 35%	2603
	11th to 20th	Day	12% 7% 2 6% 6% 3 6% 6% 6% 9% 37%	2700
	21st to end	Day	3 3 2 3 4 2 4 5% 6% 8% 59%	2700
July	1st to 10th	Day	3 3 1 3 3 3 4 5% 7% 9% 59%	2700
	11th to 20th	Day	2 2 1 3 5% 3 4 4 5% 7% 64%	2615
	21st to end	Day	4 3 1 3 4 2 5% 4 5% 7% 62%	2545
August	1st to 10th	Day	7% 3 2 4 4 4 5% 6% 6% 8% 52%	2328
	11th to 20th	Day	3 2 2 3 3 3 3 4 5% 8% 63%	2299
	21st to end	Day	4 3 1 3 3 3 4 4 6% 7% 60%	2561
September	1st to 10th	Day	6% 5% 2 3 4 2 4 3 4 6% 61%	2152
	11th to 20th	Day	7% 6% 2 4 4 3 4 4 5% 7% 56%	1980
	21st to end	Day	7% 7% 2 3 4 3 3 5% 5% 9% 54%	1980
October	1st to 10th	Day	10% 12% 2 5% 5% 2 5% 5% 5% 7% 42%	1832
	11th to 20th	Day	7% 9% 4 7% 5% 3 4 4 5% 5% 47%	1800
	21st to end	Day	4 11% 5% 8% 6% 3 5% 5% 5% 6% 42%	1931
November	1st to 10th	Day	8% 10% 6% 10% 7% 4 5% 5% 5% 6% 34%	1620
	11th to 20th	Day	3 13% 7% 9% 7% 4 4 6% 6% 7% 34%	1520
	21st to end	Day	3 9% 6% 12% 8% 5% 5% 5% 4 5% 37%	1520
December	1st to 10th	Day	3 9% 7% 12% 13% 5% 7% 7% 5% 5% 28%	1520
	11th to 20th	Day	3 12% 8% 15% 10% 5% 6% 6% 7% 7% 22%	1917
	21st to end	Day	2 12% 8% 12% 10% 4 5% 5% 4 7% 31%	2442
January	1st to 10th	Night	3 11% 6% 14% 12% 6% 7% 6% 5% 7% 24%	2836
	11th to 20th	Night	2 11% 7% 12% 11% 4 5% 6% 5% 8% 28%	2493
	21st to end	Night	2 13% 7% 13% 10% 4 6% 6% 6% 7% 26%	2574
February	1st to 10th	Night	3 12% 8% 15% 9% 5% 6% 5% 6% 7% 25%	2340
	11th to 20th	Night	3 11% 7% 14% 10% 6% 6% 6% 6% 6% 26%	2272
	21st to end	Night	2 9% 7% 16% 12% 7% 6% 5% 5% 7% 23%	1841
March	1st to 10th	Night	2 11% 6% 12% 8% 5% 6% 6% 6% 7% 32%	2026
	11th to 20th	Night	2 10% 5% 8% 7% 4 5% 7% 7% 8% 38%	1980
	21st to end	Night	3 13% 7% 13% 7% 4 5% 6% 6% 9% 28%	2178
April	1st to 10th	Night	6% 13% 7% 9% 7% 4 5% 4 6% 7% 32%	1882
	11th to 20th	Night	5% 8% 5% 8% 6% 4 5% 7% 7% 7% 37%	1629
	21st to end	Night	7% 11% 4 5% 4 3 5% 5% 7% 8% 40%	1620
May	1st to 10th	Night	5% 10% 4 6% 5% 4 6% 6% 7% 8% 39%	1620
	11th to 20th	Night	7% 5% 2 5% 7% 4 6% 6% 8% 10% 41%	1486
	21st to end	Night	13% 9% 3 6% 6% 4 7% 6% 7% 8% 30%	1552
June	1st to 10th	Night	11% 6% 2 5% 5% 3 5% 5% 7% 8% 42%	1352
	11th to 20th	Night	9% 4 2 5% 6% 3 5% 5% 7% 9% 47%	1260
	21st to end	Night	3 2 1 3 3 2 4 4 6% 8% 65%	1260
July	1st to 10th	Night	2 2 1 2 3 2 4 4 8% 9% 62%	1260
	11th to 20th	Night	2 1 1 2 2 2 4 5% 4 8% 69%	1340
	21st to end	Night	3 2 1 3 3 3 4 5% 6% 8% 63%	1773
August	1st to 10th	Night	5% 3 1 5% 4 3 5% 6% 7% 10% 52%	1611
	11th to 20th	Night	2 2 1 2 3 3 3 5% 6% 8% 64%	1602
	21st to end	Night	4 2 2 3 4 2 4 4 6% 7% 62%	1794
September	1st to 10th	Night	5% 3 2 4 3 2 4 4 4 6% 63%	1804
	11th to 20th	Night	5% 4 2 4 4 2 4 6% 6% 7% 56%	1980
	21st to end	Night	7% 6% 2 3 4 3 3 3 4 6% 60%	1980
October	1st to 10th	Night	9% 8% 2 4 4 3 4 4 5% 7% 50%	2128
	11th to 20th	Night	8% 9% 3 5% 4 2 3 4 4 6% 53%	2160
	21st to end	Night	5% 9% 4 7% 6% 3 4 5% 5% 8% 45%	2423
November	1st to 10th	Night	7% 11% 4 10% 8% 4 4 5% 6% 7% 35%	2438
	11th to 20th	Night	4 11% 5% 10% 7% 4 6% 5% 7% 7% 34%	2660
	21st to end	Night	2 8% 6% 9% 8% 4 5% 5% 6% 8% 40%	2660
December	1st to 10th	Night	3 9% 6% 13% 11% 6% 8% 4 5% 7% 28%	2660
	11th to 20th	Night	2 9% 7% 13% 11% 6% 7% 6% 8% 7% 27%	3275
	21st to end	Night	2 9% 10% 14% 10% 5% 5% 5% 5% 6% 30%	5214

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	62% 8% 14% 11% 4 1	1333
	11th to 20th	Day	56% 8% 14% 13% 7% 2	1569
	21st to end	Day	63% 6% 11% 11% 7% 2	1782
February	1st to 10th	Day	66% 7% 11% 12% 4	1620
	11th to 20th	Day	64% 7% 13% 11% 3 1	1584
	21st to end	Day	70% 6% 7% 10% 5% 2	1412
March	1st to 10th	Day	61% 9% 11% 13% 4 1	1933
	11th to 20th	Day	53% 10% 14% 14% 7% 2	1980
	21st to end	Day	65% 8% 13% 11% 2	2178
April	1st to 10th	Day	61% 6% 13% 13% 7%	2078
	11th to 20th	Day	56% 8% 13% 18% 4 1	2279
	21st to end	Day	54% 9% 13% 20% 4	2340
May	1st to 10th	Day	50% 8% 13% 22% 7%	2340
	11th to 20th	Day	44% 11% 20% 21% 5%	2410
	21st to end	Day	55% 11% 15% 14% 4	2724
June	1st to 10th	Day	44% 10% 19% 22% 5%	2603
	11th to 20th	Day	42% 9% 13% 17% 15% 4	2700
	21st to end	Day	21% 6% 11% 29% 25% 7%	2700
July	1st to 10th	Day	18% 6% 12% 26% 27% 10%	2626
	11th to 20th	Day	19% 5% 8% 20% 27% 21%	2534
	21st to end	Day	21% 5% 8% 19% 29% 18%	2404
August	1st to 10th	Day	28% 6% 10% 20% 25% 11%	2313
	11th to 20th	Day	19% 6% 10% 27% 29% 9%	2299
	21st to end	Day	22% 5% 10% 25% 30% 9%	2561
September	1st to 10th	Day	25% 4 8% 20% 34% 9%	2152
	11th to 20th	Day	29% 5% 11% 25% 23% 7%	1980
	21st to end	Day	29% 7% 13% 30% 18% 4	1980
October	1st to 10th	Day	42% 7% 14% 22% 12% 2	1832
	11th to 20th	Day	41% 7% 17% 26% 8% 1	1800
	21st to end	Day	43% 10% 16% 21% 8% 2	1931
November	1st to 10th	Day	51% 8% 14% 19% 7% 1	1620
	11th to 20th	Day	51% 10% 17% 16% 4 2	1520
	21st to end	Day	51% 8% 15% 16% 10% 1	1520
December	1st to 10th	Day	60% 9% 10% 11% 7% 3	1520
	11th to 20th	Day	61% 9% 12% 14% 3	1915
	21st to end	Day	54% 5% 9% 15% 6% 10%	2442
January	1st to 10th	Night	63% 9% 11% 11% 6% 1	2836
	11th to 20th	Night	57% 9% 12% 13% 6% 3	2493
	21st to end	Night	60% 8% 13% 11% 6% 2	2574
February	1st to 10th	Night	64% 7% 9% 14% 5% 1	2340
	11th to 20th	Night	61% 8% 11% 13% 6% 1	2273
	21st to end	Night	64% 7% 10% 9% 7% 3	1841
March	1st to 10th	Night	53% 10% 14% 16% 6% 2	2026
	11th to 20th	Night	42% 12% 16% 20% 7% 2	1980
	21st to end	Night	55% 8% 17% 16% 4 1	2178
April	1st to 10th	Night	54% 7% 16% 14% 8% 1	1882
	11th to 20th	Night	42% 10% 18% 24% 6% 1	1629
	21st to end	Night	41% 10% 17% 26% 7%	1620
May	1st to 10th	Night	39% 9% 18% 26% 7%	1620
	11th to 20th	Night	36% 11% 22% 22% 9%	1487
	21st to end	Night	47% 12% 18% 17% 6%	1552
June	1st to 10th	Night	37% 12% 19% 25% 7% 1	1352
	11th to 20th	Night	33% 8% 15% 23% 18% 4	1260
	21st to end	Night	16% 6% 13% 32% 24% 9%	1260
July	1st to 10th	Night	15% 7% 13% 27% 27% 11%	1225
	11th to 20th	Night	13% 3 12% 24% 27% 22%	1298
	21st to end	Night	17% 5% 9% 21% 30% 18%	1674
August	1st to 10th	Night	24% 7% 14% 22% 22% 11%	1602
	11th to 20th	Night	15% 5% 11% 28% 30% 11%	1602
	21st to end	Night	20% 5% 11% 22% 32% 10%	1794
September	1st to 10th	Night	22% 5% 9% 20% 32% 11%	1804
	11th to 20th	Night	24% 7% 14% 24% 24% 6%	1980
	21st to end	Night	27% 5% 12% 32% 21% 4	1980
October	1st to 10th	Night	34% 6% 16% 25% 16% 2	2128
	11th to 20th	Night	34% 6% 16% 31% 11% 2	2160
	21st to end	Night	38% 10% 18% 22% 11% 1	2423
November	1st to 10th	Night	49% 9% 15% 18% 8% 1	2438
	11th to 20th	Night	50% 10% 18% 15% 6% 2	2660
	21st to end	Night	44% 9% 17% 16% 12% 2	2660
December	1st to 10th	Night	61% 7% 13% 10% 7% 2	2660
	11th to 20th	Night	59% 10% 12% 14% 4 1	3276
	21st to end	Night	55% 7% 9% 15% 6% 8%	5214

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	13% 31% 24% 22% 9%	180
	11th to 20th	Day	12% 27% 32% 16% 7% 6%	212
	21st to end	Day	12% 24% 36% 20% 6% 1	264
February	1st to 10th	Day	21% 33% 30% 15% 1	240
	11th to 20th	Day	19% 27% 32% 17% 5% 1	240
	21st to end	Day	18% 32% 30% 17% 3	278
March	1st to 10th	Day	19% 33% 34% 12% 2	420
	11th to 20th	Day	13% 29% 33% 18% 7%	420
	21st to end	Day	18% 30% 33% 15% 4 1	462
April	1st to 10th	Day	22% 30% 31% 12% 4 1	420
	11th to 20th	Day	20% 30% 32% 13% 5%	412
	21st to end	Day	22% 21% 28% 19% 7% 3	420
May	1st to 10th	Day	16% 18% 30% 25% 10% 2	423
	11th to 20th	Day	14% 13% 31% 25% 14% 3	553
	21st to end	Day	18% 16% 24% 24% 14% 4	679
June	1st to 10th	Day	13% 16% 24% 27% 16% 5%	630
	11th to 20th	Day	18% 21% 31% 21% 8% 1	630
	21st to end	Day	7% 12% 31% 31% 17% 2	630
July	1st to 10th	Day	4 12% 31% 32% 19% 3	621
	11th to 20th	Day	3 12% 40% 29% 15% 1	582
	21st to end	Day	5% 10% 36% 31% 15% 4	487
August	1st to 10th	Day	8% 11% 33% 30% 14% 3	447
	11th to 20th	Day	6% 11% 26% 37% 15% 5%	437
	21st to end	Day	6% 15% 34% 27% 14% 4	495
September	1st to 10th	Day	8% 13% 37% 27% 13% 3	450
	11th to 20th	Day	15% 15% 31% 24% 12% 3	450
	21st to end	Day	13% 18% 33% 22% 13% 1	450
October	1st to 10th	Day	15% 17% 26% 24% 14% 5%	302
	11th to 20th	Day	18% 24% 23% 18% 11% 6%	270
	21st to end	Day	17% 23% 35% 18% 6% 1	297
November	1st to 10th	Day	19% 29% 30% 13% 7% 3	270
	11th to 20th	Day	14% 29% 33% 19% 4 1	270
	21st to end	Day	13% 21% 37% 20% 8%	270
December	1st to 10th	Day	16% 24% 30% 20% 9% 1	270
	11th to 20th	Day	14% 36% 26% 20% 4 1	266
	21st to end	Day	18% 32% 22% 17% 9% 2	198
January	1st to 10th	Night	11% 21% 29% 29% 9% 1	950
	11th to 20th	Night	10% 22% 32% 23% 11% 2	751
	21st to end	Night	9% 17% 39% 25% 9% 2	792
February	1st to 10th	Night	12% 24% 36% 23% 5% 1	720
	11th to 20th	Night	12% 23% 31% 26% 7% 1	704
	21st to end	Night	11% 21% 35% 23% 9% 2	592
March	1st to 10th	Night	9% 20% 37% 25% 8% 1	720
	11th to 20th	Night	10% 16% 30% 31% 12% 1	720
	21st to end	Night	11% 14% 33% 31% 9% 1	792
April	1st to 10th	Night	16% 17% 34% 24% 8% 2	622
	11th to 20th	Night	12% 17% 36% 26% 9%	533
	21st to end	Night	15% 8% 29% 33% 14% 1	540
May	1st to 10th	Night	11% 12% 27% 34% 15% 1	540
	11th to 20th	Night	10% 9% 28% 32% 18% 2	531
	21st to end	Night	16% 11% 23% 32% 17% 1	584
June	1st to 10th	Night	14% 7% 22% 32% 23% 1	452
	11th to 20th	Night	10% 11% 33% 32% 13%	360
	21st to end	Night	4 2 19% 49% 24% 3	360
July	1st to 10th	Night	3 1 15% 46% 33% 2	350
	11th to 20th	Night	3 2 21% 49% 24% 1	395
	21st to end	Night	3 3 19% 48% 25% 3	591
August	1st to 10th	Night	6% 3 17% 42% 30% 1	537
	11th to 20th	Night	3 3 17% 45% 30% 2	534
	21st to end	Night	5% 6% 21% 38% 28% 2	594
September	1st to 10th	Night	7% 4 22% 41% 24% 3	544
	11th to 20th	Night	7% 6% 22% 37% 25% 5%	720
	21st to end	Night	13% 7% 22% 34% 21% 4	720
October	1st to 10th	Night	13% 8% 23% 35% 19% 2	720
	11th to 20th	Night	15% 11% 25% 30% 15% 3	720
	21st to end	Night	13% 15% 30% 31% 8% 4	792
November	1st to 10th	Night	18% 17% 32% 23% 9% 1	773
	11th to 20th	Night	13% 24% 32% 25% 6%	950
	21st to end	Night	10% 19% 35% 27% 9% 1	950
December	1st to 10th	Night	14% 23% 29% 26% 7% 1	950
	11th to 20th	Night	12% 24% 31% 25% 8% 1	950
	21st to end	Night	14% 23% 33% 20% 9% 1	1045

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