Golden Spike National Historical Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Golden Spike National Historical Park clear sky chart from 2005-11-06 to 2026-03-03.

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% 6% 2 6% 4 4 4 3 5% 7% 53%	140037
	Night	7% 7% 3 6% 4 4 4 3 5% 6% 49%	138510
Transparency	Day	31% 5% 9% 20% 20% 14%	134750
	Night	34% 5% 11% 21% 18% 11%	134801
Seeing	Day	9% 6% 19% 33% 25% 9%	16643
	Night	11% 4 15% 40% 26% 4	26635

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	10% 15% 5% 13% 8% 6% 5% 4 4 4 25%	4761
	11th to 20th	Day	5% 8% 4 9% 9% 7% 6% 4 5% 6% 38%	5340
	21st to end	Day	7% 12% 4 12% 9% 6% 5% 3 5% 6% 31%	5844
February	1st to 10th	Day	11% 13% 4 11% 7% 5% 5% 4 5% 6% 29%	1890
	11th to 20th	Day	10% 12% 4 9% 6% 4 5% 4 7% 8% 30%	1943
	21st to end	Day	6% 11% 5% 11% 5% 5% 5% 4 6% 7% 35%	1730
March	1st to 10th	Day	6% 12% 4 9% 5% 4 4 4 5% 8% 39%	4753
	11th to 20th	Day	6% 8% 3 6% 4 4 4 4 6% 8% 48%	5000
	21st to end	Day	9% 12% 4 9% 5% 5% 5% 4 7% 8% 33%	5486
April	1st to 10th	Day	8% 8% 3 7% 4 5% 4 3 6% 7% 45%	2230
	11th to 20th	Day	7% 7% 2 6% 5% 4 4 4 6% 7% 48%	2562
	21st to end	Day	7% 6% 2 7% 4 4 4 4 6% 9% 47%	2600
May	1st to 10th	Day	5% 6% 2 5% 4 4 4 3 5% 7% 54%	5880
	11th to 20th	Day	5% 5% 2 7% 4 5% 5% 4 7% 8% 49%	5841
	21st to end	Day	4 4 2 4 4 3 4 3 5% 7% 60%	6423
June	1st to 10th	Day	4 4 1 4 4 3 5% 3 7% 8% 58%	2680
	11th to 20th	Day	5% 4 2 4 3 3 3 3 5% 8% 60%	2996
	21st to end	Day	2 2 1 3 2 2 2 3 4 6% 72%	2826
July	1st to 10th	Day	2 2 1 2 2 2 3 2 3 5% 77%	6319
	11th to 20th	Day	2 2 1 3 2 3 3 3 5% 6% 70%	6042
	21st to end	Day	2 2 1 3 2 2 3 3 4 6% 73%	6401
August	1st to 10th	Day	3 2 1 3 2 2 2 2 4 6% 72%	5779
	11th to 20th	Day	2 2 1 3 2 2 3 3 5% 6% 72%	5798
	21st to end	Day	5% 3 1 4 3 3 3 3 5% 6% 63%	6468
September	1st to 10th	Day	3 3 1 3 2 3 3 3 4 6% 70%	2247
	11th to 20th	Day	4 3 1 4 3 3 3 3 4 6% 66%	2200
	21st to end	Day	6% 2 1 3 2 3 2 2 5% 6% 68%	2200
October	1st to 10th	Day	5% 3 1 3 2 3 3 3 4 5% 67%	3478
	11th to 20th	Day	4 5% 2 4 3 3 3 3 5% 7% 61%	3250
	21st to end	Day	5% 5% 2 5% 3 3 4 3 4 7% 59%	3406
November	1st to 10th	Day	7% 9% 4 7% 4 3 4 4 5% 7% 47%	1854
	11th to 20th	Day	10% 7% 2 6% 3 3 4 4 7% 9% 45%	1890
	21st to end	Day	8% 11% 3 6% 4 4 5% 3 5% 6% 43%	1751
December	1st to 10th	Day	6% 8% 3 8% 6% 5% 5% 2 4 7% 45%	2700
	11th to 20th	Day	10% 11% 4 10% 7% 6% 7% 5% 6% 7% 26%	3106
	21st to end	Day	12% 14% 5% 13% 7% 5% 5% 4 5% 5% 25%	4363
January	1st to 10th	Night	10% 13% 4 8% 5% 6% 5% 4 6% 7% 33%	8086
	11th to 20th	Night	6% 9% 3 8% 5% 5% 4 4 6% 7% 43%	7650
	21st to end	Night	7% 10% 4 10% 7% 4 4 3 5% 7% 40%	8370
February	1st to 10th	Night	11% 13% 4 8% 5% 5% 5% 3 6% 7% 33%	2730
	11th to 20th	Night	9% 12% 3 8% 5% 4 5% 3 5% 6% 39%	2563
	21st to end	Night	6% 11% 3 8% 6% 5% 4 4 5% 7% 40%	2076
March	1st to 10th	Night	9% 13% 3 7% 4 4 5% 4 6% 6% 39%	5185
	11th to 20th	Night	5% 9% 3 7% 4 4 5% 5% 7% 7% 42%	5000
	21st to end	Night	8% 8% 3 8% 5% 5% 5% 4 6% 7% 39%	5489
April	1st to 10th	Night	8% 10% 3 7% 4 4 4 3 6% 6% 45%	2165
	11th to 20th	Night	9% 8% 2 7% 4 4 4 3 5% 5% 48%	1786
	21st to end	Night	9% 7% 3 6% 5% 4 3 3 6% 6% 48%	1800
May	1st to 10th	Night	7% 6% 2 5% 3 4 3 3 5% 6% 55%	4100
	11th to 20th	Night	8% 5% 2 5% 4 4 4 4 5% 7% 54%	4074
	21st to end	Night	7% 4 2 5% 4 4 4 3 5% 6% 56%	4474
June	1st to 10th	Night	5% 4 2 4 3 4 5% 4 6% 8% 55%	1708
	11th to 20th	Night	6% 4 2 4 3 3 4 4 5% 8% 58%	1400
	21st to end	Night	3 2 1 3 3 2 3 2 5% 6% 69%	1562
July	1st to 10th	Night	3 3 1 4 3 3 3 3 4 5% 68%	3640
	11th to 20th	Night	2 3 1 5% 4 4 4 4 6% 7% 59%	3915
	21st to end	Night	2 2 1 5% 3 4 4 3 5% 7% 64%	4472
August	1st to 10th	Night	2 3 1 3 2 4 5% 4 6% 7% 63%	4033
	11th to 20th	Night	3 3 2 5% 4 4 4 3 4 5% 63%	4051
	21st to end	Night	4 4 2 5% 4 4 4 4 4 6% 61%	4509
September	1st to 10th	Night	3 3 1 4 3 3 4 3 4 5% 68%	2148
	11th to 20th	Night	5% 3 1 4 2 3 4 2 4 5% 67%	2200
	21st to end	Night	6% 3 1 4 2 2 2 2 3 3 70%	2200
October	1st to 10th	Night	4 3 1 3 2 2 2 2 3 5% 73%	3718
	11th to 20th	Night	7% 6% 2 4 3 3 3 3 5% 6% 57%	3898
	21st to end	Night	5% 5% 2 5% 4 4 4 4 5% 7% 55%	4377
November	1st to 10th	Night	9% 7% 2 6% 4 4 4 3 5% 7% 50%	2665
	11th to 20th	Night	8% 8% 2 6% 4 4 3 4 6% 7% 48%	2730
	21st to end	Night	6% 9% 3 7% 5% 5% 4 3 6% 7% 46%	2843
December	1st to 10th	Night	6% 6% 3 6% 3 4 3 2 4 7% 55%	4710
	11th to 20th	Night	11% 11% 4 9% 6% 5% 5% 3 5% 7% 34%	5321
	21st to end	Night	11% 11% 4 11% 7% 6% 5% 4 6% 7% 28%	6862

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% 6% 16% 10% 5%	4762
	11th to 20th	Day	45% 8% 13% 23% 9% 2	5340
	21st to end	Day	54% 7% 10% 19% 10% 1	5844
February	1st to 10th	Day	56% 6% 14% 16% 6% 1	1890
	11th to 20th	Day	49% 8% 14% 19% 8% 2	1952
	21st to end	Day	46% 8% 13% 22% 10% 2	1730
March	1st to 10th	Day	43% 6% 9% 28% 10% 4	4753
	11th to 20th	Day	33% 5% 10% 33% 18% 1	5000
	21st to end	Day	46% 6% 19% 23% 5%	5486
April	1st to 10th	Day	38% 6% 13% 27% 13% 4	2230
	11th to 20th	Day	34% 6% 10% 28% 20% 2	2565
	21st to end	Day	33% 6% 11% 28% 20% 2	2600
May	1st to 10th	Day	28% 4 11% 26% 27% 5%	5880
	11th to 20th	Day	29% 5% 7% 28% 24% 7%	5844
	21st to end	Day	22% 5% 6% 24% 37% 6%	6424
June	1st to 10th	Day	22% 6% 10% 25% 31% 7%	2680
	11th to 20th	Day	22% 4 8% 17% 30% 19%	2996
	21st to end	Day	13% 3 4 13% 33% 34%	2826
July	1st to 10th	Day	11% 2 2 9% 16% 59%	6251
	11th to 20th	Day	14% 3 2 7% 27% 48%	5969
	21st to end	Day	12% 3 2 7% 31% 44%	6217
August	1st to 10th	Day	17% 3 4 13% 29% 34%	4208
	11th to 20th	Day	16% 3 4 14% 36% 27%	4197
	21st to end	Day	15% 2 4 14% 33% 32%	4663
September	1st to 10th	Day	17% 3 5% 16% 30% 29%	2247
	11th to 20th	Day	19% 4 6% 20% 30% 20%	2200
	21st to end	Day	18% 3 8% 22% 37% 13%	2200
October	1st to 10th	Day	20% 4 6% 18% 32% 20%	3478
	11th to 20th	Day	23% 4 8% 33% 26% 6%	3250
	21st to end	Day	25% 4 15% 37% 18% 1	3406
November	1st to 10th	Day	37% 6% 15% 25% 16% 1	1854
	11th to 20th	Day	35% 6% 21% 29% 9% 1	1890
	21st to end	Day	40% 5% 19% 26% 9% 1	1751
December	1st to 10th	Day	39% 6% 21% 26% 7% 1	2700
	11th to 20th	Day	54% 7% 19% 18% 2	3104
	21st to end	Day	59% 7% 12% 14% 7%	4363
January	1st to 10th	Night	48% 7% 18% 20% 6%	8086
	11th to 20th	Night	39% 7% 16% 29% 9% 1	7650
	21st to end	Night	45% 5% 14% 22% 13% 1	8370
February	1st to 10th	Night	50% 7% 16% 20% 6% 1	2730
	11th to 20th	Night	45% 5% 14% 21% 13% 2	2564
	21st to end	Night	43% 5% 12% 26% 12% 2	2076
March	1st to 10th	Night	44% 6% 9% 24% 12% 5%	5185
	11th to 20th	Night	38% 5% 10% 26% 20% 1	5000
	21st to end	Night	41% 6% 18% 24% 10% 1	5489
April	1st to 10th	Night	39% 5% 11% 24% 15% 6%	2165
	11th to 20th	Night	36% 5% 10% 23% 23% 4	1786
	21st to end	Night	36% 4 10% 24% 22% 4	1800
May	1st to 10th	Night	28% 4 11% 21% 28% 7%	4097
	11th to 20th	Night	28% 4 6% 25% 30% 7%	4075
	21st to end	Night	27% 4 6% 20% 35% 6%	4474
June	1st to 10th	Night	26% 5% 10% 21% 29% 9%	1708
	11th to 20th	Night	22% 5% 7% 17% 30% 18%	1400
	21st to end	Night	16% 3 3 13% 27% 37%	1562
July	1st to 10th	Night	19% 3 3 8% 15% 53%	3600
	11th to 20th	Night	22% 4 2 6% 22% 44%	3866
	21st to end	Night	20% 4 2 6% 26% 42%	4344
August	1st to 10th	Night	20% 5% 4 10% 27% 34%	2928
	11th to 20th	Night	23% 3 4 13% 27% 30%	2928
	21st to end	Night	17% 3 5% 10% 26% 39%	3245
September	1st to 10th	Night	18% 3 5% 13% 24% 36%	2148
	11th to 20th	Night	20% 3 5% 16% 30% 26%	2200
	21st to end	Night	21% 2 4 18% 32% 23%	2200
October	1st to 10th	Night	17% 2 5% 15% 34% 27%	3718
	11th to 20th	Night	29% 3 4 26% 29% 9%	3898
	21st to end	Night	28% 4 9% 34% 21% 4	4377
November	1st to 10th	Night	34% 5% 13% 27% 19% 3	2665
	11th to 20th	Night	35% 5% 14% 30% 14% 1	2730
	21st to end	Night	37% 5% 15% 31% 10% 2	2843
December	1st to 10th	Night	31% 4 15% 39% 10% 1	4710
	11th to 20th	Night	49% 6% 22% 19% 3	5322
	21st to end	Night	54% 6% 17% 15% 7%	6862

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	18% 4 17% 33% 17% 11%	228
	11th to 20th	Day	13% 3 16% 34% 25% 9%	330
	21st to end	Day	16% 4 14% 34% 25% 9%	363
February	1st to 10th	Day	19% 4 19% 35% 15% 7%	330
	11th to 20th	Day	12% 7% 20% 41% 15% 4	428
	21st to end	Day	10% 6% 24% 37% 20% 4	446
March	1st to 10th	Day	12% 6% 16% 37% 24% 6%	509
	11th to 20th	Day	8% 4 18% 39% 25% 8%	500
	21st to end	Day	16% 7% 18% 37% 20% 3	550
April	1st to 10th	Day	13% 8% 18% 35% 20% 7%	500
	11th to 20th	Day	10% 15% 26% 28% 16% 6%	492
	21st to end	Day	12% 9% 25% 30% 19% 4	500
May	1st to 10th	Day	7% 12% 27% 29% 21% 3	503
	11th to 20th	Day	11% 11% 23% 26% 21% 9%	528
	21st to end	Day	9% 8% 20% 28% 24% 11%	573
June	1st to 10th	Day	4 6% 23% 29% 26% 11%	610
	11th to 20th	Day	8% 6% 24% 33% 24% 5%	730
	21st to end	Day	3 5% 25% 36% 25% 6%	556
July	1st to 10th	Day	3 3 20% 39% 27% 8%	526
	11th to 20th	Day	4 2 19% 38% 29% 8%	524
	21st to end	Day	4 2 12% 37% 37% 9%	575
August	1st to 10th	Day	6% 3 18% 35% 28% 10%	527
	11th to 20th	Day	3 4 14% 33% 33% 11%	517
	21st to end	Day	5% 5% 12% 28% 32% 17%	583
September	1st to 10th	Day	3 4 13% 28% 34% 18%	530
	11th to 20th	Day	6% 5% 18% 31% 28% 12%	530
	21st to end	Day	8% 5% 16% 26% 33% 13%	530
October	1st to 10th	Day	7% 5% 20% 27% 27% 14%	460
	11th to 20th	Day	8% 7% 21% 26% 21% 17%	330
	21st to end	Day	9% 8% 22% 34% 22% 6%	363
November	1st to 10th	Day	15% 7% 18% 31% 21% 8%	330
	11th to 20th	Day	11% 6% 21% 35% 21% 7%	330
	21st to end	Day	14% 5% 14% 35% 25% 7%	330
December	1st to 10th	Day	13% 3 20% 33% 20% 11%	330
	11th to 20th	Day	17% 3 13% 41% 22% 3	330
	21st to end	Day	22% 7% 19% 29% 18% 6%	322
January	1st to 10th	Night	18% 4 13% 39% 22% 5%	840
	11th to 20th	Night	17% 3 14% 36% 24% 6%	840
	21st to end	Night	16% 3 13% 41% 22% 5%	924
February	1st to 10th	Night	17% 3 18% 41% 18% 2	840
	11th to 20th	Night	15% 4 16% 42% 21% 2	824
	21st to end	Night	10% 7% 18% 43% 19% 2	692
March	1st to 10th	Night	16% 5% 16% 42% 18% 4	808
	11th to 20th	Night	11% 5% 15% 43% 24% 3	800
	21st to end	Night	13% 5% 18% 44% 19% 2	880
April	1st to 10th	Night	12% 7% 19% 39% 21% 3	800
	11th to 20th	Night	12% 8% 21% 39% 17% 3	598
	21st to end	Night	13% 6% 19% 39% 21% 3	600
May	1st to 10th	Night	11% 6% 23% 39% 20% 2	600
	11th to 20th	Night	11% 6% 16% 33% 31% 4	591
	21st to end	Night	12% 7% 14% 32% 30% 5%	650
June	1st to 10th	Night	6% 8% 15% 35% 33% 3	598
	11th to 20th	Night	9% 6% 22% 36% 27% 2	400
	21st to end	Night	5% 2 19% 43% 27% 4	400
July	1st to 10th	Night	4 2 18% 36% 36% 4	390
	11th to 20th	Night	4 3 14% 47% 31% 1	506
	21st to end	Night	3 2 10% 43% 38% 5%	657
August	1st to 10th	Night	5% 2 12% 45% 33% 2	597
	11th to 20th	Night	4 3 12% 42% 36% 3	594
	21st to end	Night	5% 3 13% 38% 34% 6%	660
September	1st to 10th	Night	5% 2 11% 37% 38% 7%	778
	11th to 20th	Night	6% 3 12% 38% 34% 7%	800
	21st to end	Night	7% 3 14% 32% 34% 9%	800
October	1st to 10th	Night	9% 3 14% 36% 34% 4	800
	11th to 20th	Night	11% 5% 13% 36% 31% 5%	800
	21st to end	Night	8% 4 17% 39% 29% 4	880
November	1st to 10th	Night	12% 5% 13% 41% 25% 4	820
	11th to 20th	Night	13% 3 15% 44% 21% 4	840
	21st to end	Night	10% 4 15% 42% 25% 4	953
December	1st to 10th	Night	15% 5% 12% 44% 22% 2	1050
	11th to 20th	Night	20% 3 14% 42% 18% 2	1050
	21st to end	Night	19% 6% 18% 38% 16% 2	975

Page generated at 2026-02-27 23:40:19. Version ac07

Copyright © 2026 Attilla Danko.