Gold River
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Gold River clear sky chart from 2005-11-06 to 2024-01-13.

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	27% 15% 4 6% 5% 3 4 3 4 5% 25%	74671
	Night	29% 16% 4 6% 5% 2 3 3 3 4 23%	75087
Transparency	Day	43% 37% 7% 8% 4 1	74351
	Night	44% 37% 6% 8% 4 1	74925
Seeing	Day	34% 14% 24% 19% 8% 2	14718
	Night	38% 8% 21% 22% 11% 1	22752

By Month

Percentage Cloud Cover NW (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	41% 23% 4 4 3 1 2 2 3 2 14%	1329
	11th to 20th	Day	34% 17% 5% 7% 5% 3 3 3 4 5% 14%	1276
	21st to end	Day	31% 21% 5% 7% 6% 3 3 3 2 3 14%	1521
February	1st to 10th	Day	34% 20% 5% 5% 4 2 4 4 4 5% 14%	1599
	11th to 20th	Day	24% 24% 5% 7% 4 2 3 2 2 4 23%	1575
	21st to end	Day	22% 26% 4 7% 5% 3 4 4 3 4 19%	1340
March	1st to 10th	Day	27% 24% 5% 8% 5% 3 4 3 3 4 15%	1880
	11th to 20th	Day	29% 27% 5% 7% 5% 2 3 3 3 3 13%	1980
	21st to end	Day	32% 25% 4 7% 4 2 3 2 2 2 15%	2178
April	1st to 10th	Day	29% 24% 6% 7% 5% 3 4 2 2 4 14%	2179
	11th to 20th	Day	28% 22% 5% 8% 5% 2 3 3 4 4 17%	2308
	21st to end	Day	31% 20% 5% 8% 5% 3 3 3 3 4 16%	2340
May	1st to 10th	Day	23% 16% 4 7% 6% 3 4 3 4 5% 24%	2460
	11th to 20th	Day	23% 14% 5% 7% 7% 3 5% 4 5% 6% 21%	2541
	21st to end	Day	26% 10% 5% 9% 6% 4 4 4 4 6% 22%	2917
June	1st to 10th	Day	30% 15% 4 7% 6% 3 4 3 4 5% 19%	2700
	11th to 20th	Day	30% 13% 5% 7% 5% 3 4 3 5% 6% 18%	2700
	21st to end	Day	28% 9% 4 6% 4 3 4 4 4 6% 29%	2700
July	1st to 10th	Day	19% 9% 3 7% 5% 3 4 4 5% 6% 35%	2700
	11th to 20th	Day	17% 8% 2 4 4 3 4 5% 5% 7% 40%	2700
	21st to end	Day	15% 6% 3 5% 4 2 3 4 5% 7% 46%	2938
August	1st to 10th	Day	14% 5% 2 4 4 2 5% 4 6% 7% 46%	2394
	11th to 20th	Day	11% 6% 2 4 5% 3 4 5% 6% 7% 48%	2298
	21st to end	Day	20% 7% 3 5% 6% 4 5% 6% 5% 7% 32%	2574
September	1st to 10th	Day	18% 7% 3 6% 5% 2 4 5% 5% 5% 40%	2218
	11th to 20th	Day	23% 9% 4 6% 5% 2 4 3 3 4 36%	2010
	21st to end	Day	29% 8% 3 4 4 3 4 3 4 5% 32%	1980
October	1st to 10th	Day	25% 11% 3 7% 4 2 4 4 3 5% 31%	1814
	11th to 20th	Day	37% 13% 2 4 4 2 4 4 4 5% 22%	1800
	21st to end	Day	38% 12% 3 5% 5% 2 3 3 4 3 21%	1794
November	1st to 10th	Day	40% 17% 4 6% 5% 1 3 3 2 4 14%	1488
	11th to 20th	Day	39% 19% 4 4 4 2 4 2 3 2 17%	1520
	21st to end	Day	38% 17% 4 6% 4 2 3 2 3 3 18%	1463
December	1st to 10th	Day	30% 14% 5% 7% 5% 3 3 2 2 5% 24%	1330
	11th to 20th	Day	40% 18% 4 5% 4 2 3 3 2 3 16%	1685
	21st to end	Day	40% 25% 4 6% 4 2 3 2 2 2 10%	2442
January	1st to 10th	Night	41% 21% 4 6% 3 2 3 2 2 3 13%	2836
	11th to 20th	Night	37% 16% 4 6% 6% 3 4 3 3 4 15%	2745
	21st to end	Night	33% 21% 4 6% 4 2 3 3 3 5% 16%	2833
February	1st to 10th	Night	34% 18% 6% 8% 5% 2 3 3 3 4 16%	2360
	11th to 20th	Night	26% 22% 4 6% 4 2 3 4 3 4 23%	2272
	21st to end	Night	24% 23% 5% 6% 5% 3 3 3 4 4 21%	1914
March	1st to 10th	Night	24% 25% 5% 8% 5% 2 3 4 4 5% 16%	2080
	11th to 20th	Night	25% 26% 5% 8% 5% 2 3 3 5% 4 15%	1979
	21st to end	Night	31% 24% 4 5% 4 2 2 3 3 4 16%	2178
April	1st to 10th	Night	24% 23% 6% 6% 5% 3 4 4 4 5% 17%	1779
	11th to 20th	Night	25% 22% 5% 6% 5% 3 4 5% 3 4 18%	1601
	21st to end	Night	28% 17% 4 8% 6% 3 4 3 3 3 21%	1620
May	1st to 10th	Night	22% 15% 4 6% 5% 2 2 3 4 6% 31%	1499
	11th to 20th	Night	20% 13% 4 7% 6% 3 7% 5% 5% 4 25%	1350
	21st to end	Night	20% 13% 4 6% 6% 3 4 4 4 6% 30%	1358
June	1st to 10th	Night	24% 14% 4 6% 5% 4 4 5% 4 6% 24%	1260
	11th to 20th	Night	23% 14% 5% 8% 5% 4 5% 5% 5% 5% 22%	1260
	21st to end	Night	21% 9% 3 5% 6% 3 3 4 6% 6% 33%	1260
July	1st to 10th	Night	15% 9% 4 7% 5% 2 4 3 5% 6% 40%	1260
	11th to 20th	Night	12% 8% 3 4 4 2 3 3 5% 7% 48%	1260
	21st to end	Night	12% 6% 3 4 4 3 3 3 4 7% 52%	1379
August	1st to 10th	Night	10% 9% 2 5% 4 2 4 4 4 6% 50%	1540
	11th to 20th	Night	10% 6% 2 4 3 2 4 5% 5% 8% 51%	1602
	21st to end	Night	19% 8% 3 6% 5% 3 4 4 5% 7% 35%	1782
September	1st to 10th	Night	16% 9% 2 4 4 2 4 5% 5% 6% 42%	1741
	11th to 20th	Night	21% 10% 4 6% 4 2 3 3 4 5% 38%	1948
	21st to end	Night	29% 10% 3 5% 4 1 3 3 3 5% 33%	1980
October	1st to 10th	Night	27% 11% 3 6% 4 2 4 4 3 5% 32%	2145
	11th to 20th	Night	36% 12% 3 6% 4 3 3 3 4 5% 22%	2160
	21st to end	Night	36% 12% 4 6% 5% 3 3 3 3 4 21%	2558
November	1st to 10th	Night	42% 15% 4 7% 4 2 4 3 2 3 13%	2590
	11th to 20th	Night	38% 20% 4 6% 4 2 2 2 2 3 17%	2660
	21st to end	Night	36% 17% 4 7% 5% 2 3 2 3 3 19%	2714
December	1st to 10th	Night	30% 16% 4 6% 5% 3 4 3 4 5% 21%	2850
	11th to 20th	Night	42% 19% 3 5% 4 2 3 2 2 3 14%	3520
	21st to end	Night	44% 21% 4 6% 4 2 2 2 2 3 10%	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	53% 38% 2 4 2	1329
	11th to 20th	Day	44% 41% 5% 4 4 3	1276
	21st to end	Day	51% 36% 3 6% 4 1	1521
February	1st to 10th	Day	51% 37% 4 6% 2 1	1599
	11th to 20th	Day	44% 36% 5% 8% 6% 1	1584
	21st to end	Day	53% 35% 4 5% 2 2	1340
March	1st to 10th	Day	50% 36% 5% 6% 3 1	1880
	11th to 20th	Day	53% 35% 4 4 3 1	1980
	21st to end	Day	52% 36% 4 5% 2	2178
April	1st to 10th	Day	52% 36% 5% 5% 2	2179
	11th to 20th	Day	47% 36% 4 7% 6%	2308
	21st to end	Day	49% 36% 4 7% 4	2340
May	1st to 10th	Day	47% 37% 5% 9% 2	2460
	11th to 20th	Day	43% 38% 7% 8% 4	2544
	21st to end	Day	47% 39% 6% 5% 2	2918
June	1st to 10th	Day	48% 37% 5% 5% 4 1	2700
	11th to 20th	Day	48% 38% 7% 6% 2	2700
	21st to end	Day	40% 37% 9% 9% 5%	2700
July	1st to 10th	Day	31% 40% 12% 12% 5%	2626
	11th to 20th	Day	25% 41% 14% 17% 4	2619
	21st to end	Day	22% 39% 11% 19% 7% 2	2775
August	1st to 10th	Day	27% 39% 14% 15% 6%	2376
	11th to 20th	Day	25% 37% 14% 13% 9% 2	2298
	21st to end	Day	34% 39% 12% 11% 4	2574
September	1st to 10th	Day	26% 38% 8% 19% 7% 2	2218
	11th to 20th	Day	33% 37% 6% 11% 11% 1	2010
	21st to end	Day	37% 38% 6% 10% 8% 1	1980
October	1st to 10th	Day	37% 37% 8% 11% 7%	1814
	11th to 20th	Day	44% 36% 6% 10% 4	1800
	21st to end	Day	44% 38% 4 6% 7% 1	1794
November	1st to 10th	Day	51% 39% 3 3 3 1	1488
	11th to 20th	Day	50% 40% 4 3 2 2	1520
	21st to end	Day	47% 39% 3 5% 5%	1463
December	1st to 10th	Day	42% 40% 6% 5% 4 2	1330
	11th to 20th	Day	52% 31% 6% 5% 4 2	1688
	21st to end	Day	66% 25% 3 4 1	2442
January	1st to 10th	Night	55% 38% 2 3 2	2836
	11th to 20th	Night	44% 41% 4 5% 3 3	2745
	21st to end	Night	47% 37% 3 4 5% 2	2833
February	1st to 10th	Night	51% 37% 3 6% 3	2360
	11th to 20th	Night	42% 37% 4 8% 8% 1	2274
	21st to end	Night	50% 35% 4 7% 3 1	1914
March	1st to 10th	Night	49% 38% 6% 6% 2	2080
	11th to 20th	Night	52% 35% 5% 4 3 2	1980
	21st to end	Night	49% 37% 5% 6% 3	2178
April	1st to 10th	Night	47% 39% 5% 6% 2	1779
	11th to 20th	Night	43% 37% 4 8% 7%	1601
	21st to end	Night	46% 36% 5% 9% 4	1620
May	1st to 10th	Night	43% 37% 5% 11% 4	1499
	11th to 20th	Night	41% 39% 9% 8% 3 1	1350
	21st to end	Night	43% 39% 9% 7% 2	1358
June	1st to 10th	Night	44% 39% 7% 6% 3 2	1260
	11th to 20th	Night	47% 39% 7% 5% 2	1260
	21st to end	Night	34% 39% 12% 8% 6% 1	1260
July	1st to 10th	Night	28% 39% 14% 12% 7%	1225
	11th to 20th	Night	22% 41% 18% 14% 5%	1218
	21st to end	Night	17% 41% 13% 21% 7% 2	1302
August	1st to 10th	Night	26% 38% 13% 18% 5%	1533
	11th to 20th	Night	20% 38% 14% 15% 11% 1	1602
	21st to end	Night	32% 39% 11% 14% 3	1782
September	1st to 10th	Night	22% 39% 10% 18% 10% 2	1741
	11th to 20th	Night	30% 38% 8% 10% 12% 2	1948
	21st to end	Night	40% 37% 7% 8% 6% 2	1980
October	1st to 10th	Night	36% 36% 7% 13% 8% 1	2145
	11th to 20th	Night	44% 36% 6% 9% 4	2160
	21st to end	Night	44% 38% 4 7% 7% 1	2558
November	1st to 10th	Night	51% 40% 3 3 3 1	2590
	11th to 20th	Night	50% 39% 3 5% 2 2	2660
	21st to end	Night	47% 40% 3 6% 4 1	2714
December	1st to 10th	Night	44% 39% 5% 6% 4 2	2850
	11th to 20th	Night	54% 33% 4 5% 3 1	3516
	21st to end	Night	66% 25% 3 3 2 1	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	51% 13% 19% 10% 6% 2	180
	11th to 20th	Day	48% 13% 22% 11% 6%	165
	21st to end	Day	44% 10% 21% 14% 9% 1	311
February	1st to 10th	Day	48% 14% 26% 11% 1	340
	11th to 20th	Day	42% 15% 28% 10% 5%	335
	21st to end	Day	45% 15% 24% 12% 4	280
March	1st to 10th	Day	40% 17% 22% 15% 5% 1	376
	11th to 20th	Day	41% 17% 22% 14% 6%	420
	21st to end	Day	48% 12% 24% 11% 4 1	462
April	1st to 10th	Day	46% 20% 19% 11% 4	420
	11th to 20th	Day	41% 16% 23% 13% 6% 2	412
	21st to end	Day	48% 18% 17% 11% 4 1	420
May	1st to 10th	Day	31% 19% 26% 18% 5% 1	423
	11th to 20th	Day	32% 12% 27% 18% 8% 3	511
	21st to end	Day	26% 15% 32% 19% 7% 1	680
June	1st to 10th	Day	39% 18% 21% 16% 5% 1	630
	11th to 20th	Day	37% 22% 21% 15% 5% 1	630
	21st to end	Day	28% 13% 24% 24% 8% 3	630
July	1st to 10th	Day	25% 12% 26% 28% 8% 2	621
	11th to 20th	Day	20% 15% 29% 26% 8% 2	618
	21st to end	Day	17% 9% 23% 34% 13% 4	684
August	1st to 10th	Day	18% 7% 20% 36% 14% 5%	489
	11th to 20th	Day	11% 7% 29% 32% 18% 4	437
	21st to end	Day	22% 14% 28% 23% 10% 3	495
September	1st to 10th	Day	26% 12% 31% 21% 10% 1	450
	11th to 20th	Day	34% 12% 21% 20% 11% 2	450
	21st to end	Day	35% 12% 20% 20% 10% 1	450
October	1st to 10th	Day	32% 14% 24% 20% 7% 4	450
	11th to 20th	Day	46% 10% 21% 13% 9% 2	450
	21st to end	Day	47% 12% 20% 10% 8% 2	401
November	1st to 10th	Day	42% 13% 23% 16% 7%	180
	11th to 20th	Day	46% 13% 12% 16% 9% 3	180
	21st to end	Day	53% 12% 12% 9% 8% 6%	180
December	1st to 10th	Day	39% 12% 19% 15% 12% 2	180
	11th to 20th	Day	43% 12% 18% 14% 10% 3	180
	21st to end	Day	48% 11% 20% 17% 4 1	198
January	1st to 10th	Night	52% 12% 20% 13% 4	850
	11th to 20th	Night	45% 9% 24% 16% 6%	815
	21st to end	Night	46% 8% 22% 18% 5% 1	880
February	1st to 10th	Night	45% 9% 27% 17% 2	728
	11th to 20th	Night	40% 8% 23% 24% 5%	704
	21st to end	Night	39% 11% 27% 17% 7% 1	592
March	1st to 10th	Night	37% 13% 23% 19% 8%	720
	11th to 20th	Night	43% 11% 20% 19% 6%	720
	21st to end	Night	44% 11% 18% 18% 8% 1	792
April	1st to 10th	Night	38% 9% 23% 22% 7% 2	653
	11th to 20th	Night	36% 10% 24% 21% 9%	533
	21st to end	Night	38% 6% 24% 23% 7%	540
May	1st to 10th	Night	28% 8% 19% 27% 16% 1	419
	11th to 20th	Night	27% 5% 18% 29% 19% 1	354
	21st to end	Night	24% 4 22% 34% 16%	389
June	1st to 10th	Night	31% 7% 18% 28% 16% 1	360
	11th to 20th	Night	28% 9% 26% 23% 14% 1	360
	21st to end	Night	24% 4 20% 32% 18% 2	360
July	1st to 10th	Night	18% 4 17% 34% 25% 2	350
	11th to 20th	Night	16% 5% 16% 36% 27% 1	348
	21st to end	Night	13% 4 13% 30% 37% 3	394
August	1st to 10th	Night	15% 4 10% 30% 36% 6%	509
	11th to 20th	Night	13% 2 10% 41% 30% 3	534
	21st to end	Night	23% 4 20% 31% 21% 1	594
September	1st to 10th	Night	21% 5% 20% 35% 18% 3	661
	11th to 20th	Night	25% 6% 17% 25% 24% 4	720
	21st to end	Night	35% 5% 20% 27% 12% 1	720
October	1st to 10th	Night	34% 4 22% 26% 13% 2	720
	11th to 20th	Night	43% 5% 21% 18% 11% 2	720
	21st to end	Night	44% 8% 23% 18% 6% 2	792
November	1st to 10th	Night	52% 7% 23% 16% 2	740
	11th to 20th	Night	50% 9% 23% 14% 3	760
	21st to end	Night	47% 10% 23% 13% 6% 1	786
December	1st to 10th	Night	40% 9% 22% 20% 7% 1	850
	11th to 20th	Night	51% 8% 22% 15% 4	850
	21st to end	Night	50% 12% 23% 14% 1	935

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