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 2026-01-02.

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	23% 15% 4 8% 4 4 3 3 4 5% 28%	131381
	Night	26% 17% 4 7% 4 3 3 2 4 4 25%	128714
Transparency	Day	59% 6% 11% 15% 8% 2	131076
	Night	63% 5% 9% 13% 8% 2	128596
Seeing	Day	34% 14% 24% 19% 8% 2	17333
	Night	37% 8% 21% 22% 11% 1	25268

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	31% 28% 4 8% 4 3 3 2 3 3 11%	3186
	11th to 20th	Day	20% 13% 3 7% 4 3 3 2 4 7% 31%	3159
	21st to end	Day	35% 18% 3 6% 3 3 2 1 2 3 23%	3843
February	1st to 10th	Day	31% 20% 5% 6% 3 3 4 3 5% 5% 16%	1777
	11th to 20th	Day	24% 24% 4 8% 3 3 2 2 2 4 24%	1755
	21st to end	Day	23% 26% 4 8% 5% 4 3 3 3 3 17%	1495
March	1st to 10th	Day	23% 25% 5% 9% 4 4 3 2 3 4 16%	4716
	11th to 20th	Day	18% 27% 6% 11% 6% 4 3 3 3 3 16%	5000
	21st to end	Day	25% 24% 5% 12% 5% 5% 4 3 3 3 12%	5486
April	1st to 10th	Day	27% 25% 5% 9% 4 4 4 2 3 3 14%	2423
	11th to 20th	Day	25% 23% 4 8% 4 3 3 2 4 4 19%	2568
	21st to end	Day	29% 21% 4 8% 4 4 3 2 3 4 18%	2600
May	1st to 10th	Day	18% 15% 4 10% 6% 5% 4 3 4 4 27%	6182
	11th to 20th	Day	21% 15% 4 8% 5% 4 5% 4 5% 7% 23%	6453
	21st to end	Day	28% 17% 5% 10% 5% 4 3 3 3 4 18%	7405
June	1st to 10th	Day	28% 15% 4 7% 5% 4 4 2 4 5% 22%	3000
	11th to 20th	Day	28% 14% 5% 9% 5% 5% 3 3 5% 6% 18%	3000
	21st to end	Day	27% 12% 3 6% 4 4 4 3 4 6% 28%	3000
July	1st to 10th	Day	11% 5% 2 6% 3 4 4 4 5% 6% 51%	6780
	11th to 20th	Day	7% 4 1 3 2 2 3 3 4 6% 64%	6780
	21st to end	Day	11% 7% 2 5% 3 3 3 3 5% 7% 49%	7375
August	1st to 10th	Day	8% 3 1 3 2 2 3 3 6% 8% 61%	4331
	11th to 20th	Day	17% 12% 4 8% 4 4 4 4 6% 6% 31%	4156
	21st to end	Day	18% 7% 2 6% 4 4 4 4 5% 7% 38%	4664
September	1st to 10th	Day	16% 7% 2 6% 4 3 4 3 5% 5% 43%	2464
	11th to 20th	Day	23% 10% 3 7% 4 3 4 3 3 5% 36%	2232
	21st to end	Day	29% 9% 3 6% 3 4 4 3 4 5% 30%	2200
October	1st to 10th	Day	32% 14% 4 9% 4 3 3 3 3 4 22%	3295
	11th to 20th	Day	34% 13% 3 7% 3 3 4 3 4 5% 21%	3261
	21st to end	Day	31% 16% 4 8% 5% 5% 4 3 4 4 16%	3200
November	1st to 10th	Day	40% 18% 4 8% 4 3 3 2 2 3 13%	1648
	11th to 20th	Day	37% 21% 4 6% 4 3 3 2 2 2 16%	1680
	21st to end	Day	37% 18% 3 7% 3 4 3 2 3 3 17%	1617
December	1st to 10th	Day	25% 17% 4 9% 5% 5% 4 2 4 6% 20%	2360
	11th to 20th	Day	40% 22% 4 7% 3 3 3 2 2 3 11%	2715
	21st to end	Day	36% 28% 5% 8% 3 3 2 2 2 2 9%	3575
January	1st to 10th	Night	34% 26% 4 8% 3 3 2 2 2 3 12%	6781
	11th to 20th	Night	23% 12% 3 6% 4 3 4 3 5% 6% 32%	6739
	21st to end	Night	37% 17% 3 5% 3 2 3 2 2 3 24%	7126
February	1st to 10th	Night	32% 18% 5% 8% 4 3 3 2 3 4 18%	2622
	11th to 20th	Night	24% 23% 4 7% 3 3 3 3 3 4 24%	2532
	21st to end	Night	24% 24% 5% 8% 4 3 3 3 4 3 19%	2133
March	1st to 10th	Night	21% 25% 5% 9% 4 3 3 2 4 4 20%	5168
	11th to 20th	Night	16% 25% 8% 12% 5% 3 3 3 4 3 18%	4999
	21st to end	Night	27% 24% 6% 9% 5% 4 4 2 3 3 13%	5489
April	1st to 10th	Night	23% 25% 5% 7% 5% 4 4 3 4 4 17%	1975
	11th to 20th	Night	22% 22% 4 7% 4 4 4 4 3 4 22%	1781
	21st to end	Night	27% 19% 4 8% 5% 4 3 2 3 4 22%	1800
May	1st to 10th	Night	14% 15% 4 8% 5% 5% 4 4 4 6% 31%	3783
	11th to 20th	Night	21% 15% 3 7% 5% 4 4 4 4 5% 28%	3438
	21st to end	Night	28% 19% 3 7% 4 3 3 3 3 4 22%	3470
June	1st to 10th	Night	23% 15% 4 7% 5% 4 4 3 4 6% 26%	1400
	11th to 20th	Night	21% 16% 5% 9% 4 5% 5% 3 5% 5% 22%	1400
	21st to end	Night	22% 11% 3 6% 5% 3 3 3 6% 6% 32%	1400
July	1st to 10th	Night	10% 6% 2 5% 4 3 4 3 6% 6% 50%	3180
	11th to 20th	Night	5% 5% 2 3 2 2 3 2 4 6% 67%	3180
	21st to end	Night	11% 7% 2 4 3 3 3 3 5% 6% 52%	3468
August	1st to 10th	Night	6% 5% 1 3 2 2 3 2 4 5% 65%	2823
	11th to 20th	Night	15% 13% 4 8% 4 3 5% 4 5% 7% 32%	2902
	21st to end	Night	16% 10% 3 7% 4 4 4 3 5% 5% 39%	3245
September	1st to 10th	Night	14% 9% 2 6% 3 4 4 4 5% 6% 43%	1935
	11th to 20th	Night	20% 10% 4 6% 4 3 3 2 4 5% 37%	2165
	21st to end	Night	30% 11% 3 6% 4 2 3 2 3 5% 30%	2200
October	1st to 10th	Night	33% 14% 4 8% 4 4 4 3 4 4 20%	3904
	11th to 20th	Night	36% 14% 4 8% 4 4 3 2 4 5% 18%	3897
	21st to end	Night	30% 15% 4 9% 5% 5% 4 3 4 4 19%	4596
November	1st to 10th	Night	42% 16% 4 7% 4 3 3 2 2 3 12%	2870
	11th to 20th	Night	36% 23% 4 7% 3 2 2 2 3 2 16%	2940
	21st to end	Night	34% 18% 3 9% 4 3 3 2 3 3 18%	3000
December	1st to 10th	Night	28% 18% 4 8% 4 3 3 2 4 4 21%	5040
	11th to 20th	Night	39% 22% 4 8% 4 3 3 2 3 3 11%	5710
	21st to end	Night	37% 26% 5% 9% 4 3 2 1 2 3 9%	7623

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	78% 4 5% 7% 5% 1	3186
	11th to 20th	Day	53% 5% 10% 17% 12% 3	3180
	21st to end	Day	70% 3 4 15% 8% 1	3843
February	1st to 10th	Day	72% 4 5% 7% 8% 3	1777
	11th to 20th	Day	67% 3 7% 10% 11% 2	1764
	21st to end	Day	73% 4 7% 8% 5% 3	1495
March	1st to 10th	Day	70% 5% 5% 12% 4 3	4716
	11th to 20th	Day	73% 4 5% 9% 9% 1	5000
	21st to end	Day	78% 6% 7% 6% 2 1	5486
April	1st to 10th	Day	77% 4 7% 8% 4 1	2423
	11th to 20th	Day	69% 5% 6% 11% 8% 1	2568
	21st to end	Day	71% 4 6% 12% 6%	2600
May	1st to 10th	Day	60% 6% 9% 18% 7%	6182
	11th to 20th	Day	58% 10% 12% 17% 3	6456
	21st to end	Day	70% 7% 10% 7% 6% 1	7406
June	1st to 10th	Day	66% 6% 9% 11% 7% 2	3000
	11th to 20th	Day	66% 7% 11% 11% 4	3000
	21st to end	Day	59% 6% 13% 14% 6%	3000
July	1st to 10th	Day	33% 7% 15% 20% 15% 9%	6706
	11th to 20th	Day	21% 7% 17% 32% 23%	6699
	21st to end	Day	33% 7% 23% 29% 7% 1	7168
August	1st to 10th	Day	22% 5% 14% 41% 16% 1	4313
	11th to 20th	Day	51% 8% 17% 14% 8% 1	4195
	21st to end	Day	44% 7% 20% 20% 9%	4663
September	1st to 10th	Day	43% 6% 14% 25% 10% 4	2464
	11th to 20th	Day	52% 5% 11% 17% 14% 2	2232
	21st to end	Day	57% 5% 11% 14% 11% 2	2200
October	1st to 10th	Day	66% 5% 10% 11% 7% 1	3295
	11th to 20th	Day	65% 4 9% 14% 7%	3261
	21st to end	Day	67% 8% 8% 10% 6% 1	3200
November	1st to 10th	Day	78% 3 6% 8% 4 1	1648
	11th to 20th	Day	77% 3 5% 6% 5% 3	1680
	21st to end	Day	75% 3 5% 7% 7% 3	1617
December	1st to 10th	Day	65% 6% 9% 12% 5% 2	2360
	11th to 20th	Day	80% 5% 5% 5% 3 2	2718
	21st to end	Day	84% 3 4 5% 2 1	3575
January	1st to 10th	Night	80% 3 5% 7% 4 1	6781
	11th to 20th	Night	53% 5% 9% 18% 12% 3	6780
	21st to end	Night	68% 3 5% 13% 10% 1	7126
February	1st to 10th	Night	72% 4 4 8% 9% 3	2622
	11th to 20th	Night	67% 3 6% 11% 9% 3	2534
	21st to end	Night	71% 5% 7% 11% 5% 2	2133
March	1st to 10th	Night	67% 5% 6% 11% 8% 3	5168
	11th to 20th	Night	70% 5% 6% 11% 8% 1	5000
	21st to end	Night	76% 5% 7% 7% 4 1	5489
April	1st to 10th	Night	71% 7% 8% 9% 4	1975
	11th to 20th	Night	66% 5% 6% 12% 11% 1	1781
	21st to end	Night	68% 3 7% 14% 7% 1	1800
May	1st to 10th	Night	51% 9% 11% 19% 9%	3780
	11th to 20th	Night	55% 9% 17% 14% 4	3438
	21st to end	Night	66% 7% 11% 11% 4 1	3470
June	1st to 10th	Night	61% 6% 13% 11% 8% 2	1400
	11th to 20th	Night	63% 8% 12% 12% 5%	1400
	21st to end	Night	52% 7% 18% 15% 7% 1	1400
July	1st to 10th	Night	35% 8% 16% 14% 21% 6%	3145
	11th to 20th	Night	19% 6% 22% 37% 16%	3138
	21st to end	Night	31% 9% 28% 25% 7% 1	3370
August	1st to 10th	Night	22% 4 12% 40% 20% 1	2816
	11th to 20th	Night	49% 10% 17% 13% 10% 1	2929
	21st to end	Night	44% 8% 18% 22% 8%	3245
September	1st to 10th	Night	41% 7% 14% 24% 12% 2	1935
	11th to 20th	Night	50% 6% 12% 14% 16% 2	2165
	21st to end	Night	58% 6% 11% 13% 9% 3	2200
October	1st to 10th	Night	66% 6% 9% 11% 7% 1	3904
	11th to 20th	Night	70% 4 8% 12% 6%	3897
	21st to end	Night	66% 7% 8% 11% 7% 1	4596
November	1st to 10th	Night	79% 4 6% 6% 5% 1	2870
	11th to 20th	Night	77% 3 5% 7% 4 3	2940
	21st to end	Night	73% 3 5% 8% 7% 4	3000
December	1st to 10th	Night	68% 3 8% 14% 5% 1	5040
	11th to 20th	Night	80% 4 5% 6% 3 1	5706
	21st to end	Night	82% 5% 5% 4 2 1	7623

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	49% 12% 20% 12% 5% 1	202
	11th to 20th	Day	42% 12% 24% 16% 7%	200
	21st to end	Day	45% 10% 20% 15% 9% 2	370
February	1st to 10th	Day	43% 12% 27% 14% 3 1	400
	11th to 20th	Day	41% 14% 27% 12% 6%	395
	21st to end	Day	47% 15% 23% 12% 3	331
March	1st to 10th	Day	41% 15% 23% 16% 4 2	446
	11th to 20th	Day	40% 16% 22% 14% 7%	500
	21st to end	Day	45% 14% 25% 11% 4 1	550
April	1st to 10th	Day	44% 20% 19% 11% 4	500
	11th to 20th	Day	38% 17% 24% 14% 6% 2	492
	21st to end	Day	45% 18% 18% 13% 4 1	500
May	1st to 10th	Day	30% 20% 27% 16% 6% 1	503
	11th to 20th	Day	34% 13% 26% 18% 7% 2	599
	21st to end	Day	28% 18% 30% 17% 6% 2	790
June	1st to 10th	Day	37% 18% 23% 16% 5% 1	730
	11th to 20th	Day	34% 22% 21% 16% 5% 1	730
	21st to end	Day	29% 13% 26% 23% 7% 2	730
July	1st to 10th	Day	23% 12% 28% 27% 8% 2	721
	11th to 20th	Day	18% 15% 30% 26% 9% 2	718
	21st to end	Day	16% 10% 25% 32% 13% 4	794
August	1st to 10th	Day	16% 7% 22% 36% 13% 6%	573
	11th to 20th	Day	15% 8% 27% 30% 17% 3	517
	21st to end	Day	21% 12% 26% 24% 12% 4	583
September	1st to 10th	Day	23% 12% 29% 24% 12% 1	530
	11th to 20th	Day	32% 12% 22% 22% 11% 2	530
	21st to end	Day	36% 15% 21% 18% 9% 1	530
October	1st to 10th	Day	33% 14% 25% 19% 6% 3	530
	11th to 20th	Day	45% 11% 22% 13% 8% 2	530
	21st to end	Day	47% 12% 21% 11% 8% 1	467
November	1st to 10th	Day	45% 13% 22% 15% 5%	220
	11th to 20th	Day	45% 15% 14% 16% 7% 3	220
	21st to end	Day	49% 11% 13% 12% 10% 5%	220
December	1st to 10th	Day	41% 11% 19% 15% 11% 4	220
	11th to 20th	Day	49% 11% 16% 12% 8% 3	220
	21st to end	Day	48% 12% 19% 17% 3	242
January	1st to 10th	Night	51% 12% 20% 13% 4	905
	11th to 20th	Night	42% 9% 25% 18% 6%	900
	21st to end	Night	46% 8% 21% 18% 5% 1	990
February	1st to 10th	Night	42% 9% 27% 19% 3	810
	11th to 20th	Night	39% 8% 23% 25% 5%	784
	21st to end	Night	40% 12% 25% 16% 6% 1	660
March	1st to 10th	Night	37% 13% 23% 20% 7%	800
	11th to 20th	Night	41% 12% 20% 21% 6%	800
	21st to end	Night	44% 12% 18% 18% 7% 1	880
April	1st to 10th	Night	37% 9% 23% 23% 6% 1	725
	11th to 20th	Night	33% 9% 26% 22% 9%	593
	21st to end	Night	38% 6% 23% 24% 8%	600
May	1st to 10th	Night	27% 7% 20% 28% 17% 1	465
	11th to 20th	Night	28% 6% 18% 29% 17% 2	394
	21st to end	Night	27% 4 21% 33% 15%	433
June	1st to 10th	Night	30% 7% 18% 29% 15% 1	400
	11th to 20th	Night	27% 10% 25% 24% 14% 1	400
	21st to end	Night	24% 6% 20% 31% 19% 2	400
July	1st to 10th	Night	17% 4 18% 34% 26% 2	390
	11th to 20th	Night	14% 4 16% 36% 28% 1	388
	21st to end	Night	13% 4 13% 29% 38% 3	438
August	1st to 10th	Night	14% 4 9% 30% 37% 6%	567
	11th to 20th	Night	16% 3 11% 39% 29% 3	594
	21st to end	Night	22% 5% 18% 30% 23% 3	660
September	1st to 10th	Night	19% 5% 19% 34% 20% 3	735
	11th to 20th	Night	25% 6% 17% 26% 24% 3	800
	21st to end	Night	36% 7% 20% 26% 10% 1	800
October	1st to 10th	Night	34% 5% 22% 25% 13% 2	800
	11th to 20th	Night	43% 5% 20% 20% 10% 2	800
	21st to end	Night	44% 8% 23% 18% 5% 1	880
November	1st to 10th	Night	52% 8% 22% 16% 2	820
	11th to 20th	Night	50% 10% 22% 15% 3	840
	21st to end	Night	45% 11% 24% 13% 6% 1	872
December	1st to 10th	Night	41% 10% 21% 19% 8% 1	950
	11th to 20th	Night	52% 9% 21% 14% 4	950
	21st to end	Night	49% 12% 24% 14% 1	1045

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