Prairie Grass Stargaze
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Prairie Grass Stargaze clear sky chart from 2005-11-06 to 2025-03-12.

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	12% 8% 3 8% 5% 4 5% 4 5% 7% 38%	109806
	Night	11% 8% 3 9% 5% 4 5% 4 5% 6% 40%	109419
Transparency	Day	43% 7% 14% 23% 12% 1	113428
	Night	42% 6% 13% 23% 14% 2	113938
Seeing	Day	16% 11% 32% 27% 12% 3	16355
	Night	14% 10% 36% 30% 9% 1	26444

By Month

Percentage Cloud Cover SE (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	6% 13% 6% 21% 10% 7% 6% 3 4 5% 18%	3617
	11th to 20th	Day	6% 12% 5% 10% 7% 6% 10% 6% 10% 7% 22%	4051
	21st to end	Day	4 12% 9% 12% 6% 5% 5% 4 5% 5% 34%	4488
February	1st to 10th	Day	8% 13% 4 11% 9% 7% 7% 5% 6% 6% 26%	1800
	11th to 20th	Day	8% 10% 5% 10% 7% 7% 6% 4 7% 6% 30%	1754
	21st to end	Day	12% 11% 3 9% 7% 4 5% 4 6% 6% 33%	1565
March	1st to 10th	Day	14% 9% 4 7% 5% 4 4 3 5% 7% 38%	3527
	11th to 20th	Day	11% 11% 3 8% 4 4 4 3 5% 7% 41%	3491
	21st to end	Day	25% 14% 6% 10% 4 3 3 3 4 5% 23%	3814
April	1st to 10th	Day	18% 9% 3 6% 4 4 5% 3 6% 7% 35%	2215
	11th to 20th	Day	20% 10% 4 7% 4 4 4 3 4 6% 34%	2361
	21st to end	Day	23% 11% 3 6% 4 4 4 3 4 5% 33%	2470
May	1st to 10th	Day	17% 7% 2 5% 4 4 5% 4 7% 8% 37%	4082
	11th to 20th	Day	15% 6% 2 6% 4 4 4 3 5% 6% 45%	4321
	21st to end	Day	18% 6% 2 6% 4 4 4 4 6% 7% 38%	4824
June	1st to 10th	Day	12% 5% 2 4 4 4 4 3 6% 8% 48%	2660
	11th to 20th	Day	15% 5% 2 6% 5% 4 4 4 6% 8% 40%	2813
	21st to end	Day	10% 5% 2 6% 4 4 4 4 7% 9% 45%	2850
July	1st to 10th	Day	9% 5% 2 6% 5% 4 6% 5% 7% 9% 41%	4750
	11th to 20th	Day	5% 3 2 4 3 3 4 4 5% 8% 58%	4450
	21st to end	Day	5% 4 2 4 4 4 5% 4 6% 9% 53%	4465
August	1st to 10th	Day	13% 6% 3 6% 4 4 5% 4 5% 6% 43%	4104
	11th to 20th	Day	13% 7% 2 6% 5% 4 5% 5% 7% 8% 39%	4041
	21st to end	Day	9% 4 2 5% 4 4 4 3 6% 8% 52%	4446
September	1st to 10th	Day	11% 5% 1 4 4 4 4 4 4 7% 51%	2280
	11th to 20th	Day	10% 5% 2 5% 4 4 4 3 4 7% 51%	2120
	21st to end	Day	13% 5% 2 5% 3 3 4 4 5% 7% 49%	2081
October	1st to 10th	Day	15% 7% 2 5% 3 4 4 2 4 6% 47%	1900
	11th to 20th	Day	14% 9% 2 6% 4 3 4 3 4 5% 46%	1900
	21st to end	Day	16% 8% 2 8% 4 3 3 2 4 7% 43%	2085
November	1st to 10th	Day	13% 9% 2 7% 3 4 3 3 5% 7% 42%	1681
	11th to 20th	Day	11% 11% 4 12% 6% 5% 4 3 5% 5% 35%	1600
	21st to end	Day	11% 10% 4 10% 5% 5% 3 3 6% 6% 37%	1600
December	1st to 10th	Day	6% 9% 5% 11% 9% 8% 4 4 6% 8% 31%	2610
	11th to 20th	Day	10% 13% 6% 11% 8% 8% 6% 4 5% 6% 23%	3008
	21st to end	Day	16% 12% 4 21% 6% 4 4 3 4 6% 20%	3982
January	1st to 10th	Night	7% 10% 4 18% 11% 7% 6% 5% 5% 5% 22%	6348
	11th to 20th	Night	4 8% 4 13% 7% 8% 11% 7% 8% 7% 23%	5928
	21st to end	Night	5% 12% 8% 12% 5% 5% 5% 3 5% 4 37%	6490
February	1st to 10th	Night	8% 12% 4 10% 7% 5% 5% 5% 5% 6% 33%	2600
	11th to 20th	Night	8% 9% 4 9% 6% 5% 6% 5% 6% 6% 36%	2533
	21st to end	Night	10% 9% 3 9% 6% 5% 5% 4 5% 7% 38%	2084
March	1st to 10th	Night	9% 8% 3 7% 4 4 3 3 4 6% 49%	3546
	11th to 20th	Night	10% 7% 2 6% 5% 4 5% 4 6% 6% 43%	3497
	21st to end	Night	28% 11% 4 9% 4 3 3 2 3 5% 27%	3817
April	1st to 10th	Night	15% 10% 3 6% 4 3 4 4 6% 6% 39%	1964
	11th to 20th	Night	17% 10% 4 6% 4 3 4 3 5% 5% 40%	1766
	21st to end	Night	18% 8% 3 6% 3 3 4 3 5% 7% 39%	1710
May	1st to 10th	Night	17% 6% 2 5% 3 3 4 3 5% 6% 45%	2823
	11th to 20th	Night	12% 5% 2 5% 4 4 4 3 5% 7% 50%	2583
	21st to end	Night	17% 6% 2 5% 3 4 3 3 5% 6% 45%	2743
June	1st to 10th	Night	8% 4 1 3 3 3 4 4 6% 8% 55%	1520
	11th to 20th	Night	10% 4 2 4 4 3 5% 5% 6% 8% 48%	1361
	21st to end	Night	7% 3 2 4 3 3 4 3 6% 7% 58%	1330
July	1st to 10th	Night	9% 4 1 5% 4 4 5% 4 7% 9% 47%	2220
	11th to 20th	Night	3 2 1 3 2 4 4 3 6% 7% 64%	2511
	21st to end	Night	4 3 1 4 3 3 4 3 6% 9% 59%	3098
August	1st to 10th	Night	13% 5% 2 4 3 3 4 3 5% 7% 51%	2836
	11th to 20th	Night	12% 5% 2 5% 3 3 3 3 6% 8% 52%	2798
	21st to end	Night	8% 4 2 5% 4 3 4 3 5% 8% 53%	3217
September	1st to 10th	Night	9% 4 2 5% 3 2 4 2 4 7% 59%	1900
	11th to 20th	Night	9% 4 2 4 3 4 3 3 5% 7% 56%	2057
	21st to end	Night	11% 4 2 4 2 3 4 3 5% 7% 55%	2090
October	1st to 10th	Night	14% 5% 2 4 3 3 3 3 4 6% 51%	2270
	11th to 20th	Night	14% 9% 2 6% 3 2 3 3 4 6% 48%	2280
	21st to end	Night	15% 9% 3 7% 3 3 3 3 4 7% 43%	2509
November	1st to 10th	Night	11% 7% 2 7% 5% 4 4 4 5% 5% 46%	2615
	11th to 20th	Night	10% 10% 3 9% 5% 4 4 4 4 5% 41%	2800
	21st to end	Night	12% 9% 3 9% 4 4 4 4 5% 6% 40%	2800
December	1st to 10th	Night	5% 8% 4 12% 8% 7% 5% 4 5% 7% 35%	4580
	11th to 20th	Night	11% 10% 5% 12% 8% 6% 5% 4 5% 6% 29%	5199
	21st to end	Night	16% 12% 5% 16% 6% 5% 5% 4 5% 5% 21%	6996

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	68% 4 9% 12% 6%	3618
	11th to 20th	Day	55% 5% 10% 18% 12%	4051
	21st to end	Day	51% 6% 16% 16% 10%	4488
February	1st to 10th	Day	56% 7% 15% 15% 8% 1	1800
	11th to 20th	Day	53% 7% 12% 18% 8% 2	1763
	21st to end	Day	48% 8% 13% 18% 11% 2	1565
March	1st to 10th	Day	45% 6% 13% 25% 11% 1	3527
	11th to 20th	Day	41% 7% 11% 26% 12% 3	3491
	21st to end	Day	63% 7% 11% 13% 6% 1	3814
April	1st to 10th	Day	47% 6% 15% 21% 9% 1	2215
	11th to 20th	Day	51% 6% 12% 19% 11% 1	2361
	21st to end	Day	52% 6% 11% 21% 9%	2470
May	1st to 10th	Day	41% 9% 14% 22% 13%	4120
	11th to 20th	Day	37% 7% 12% 26% 15% 3	4325
	21st to end	Day	42% 9% 13% 25% 11% 1	4837
June	1st to 10th	Day	34% 8% 16% 27% 14% 1	2660
	11th to 20th	Day	41% 8% 13% 21% 15% 2	2813
	21st to end	Day	35% 8% 15% 27% 13% 2	2850
July	1st to 10th	Day	36% 9% 21% 23% 11% 1	4676
	11th to 20th	Day	23% 7% 15% 34% 18% 3	4373
	21st to end	Day	27% 8% 17% 29% 18% 1	4325
August	1st to 10th	Day	40% 7% 11% 28% 12% 2	4090
	11th to 20th	Day	40% 9% 15% 28% 8% 1	4080
	21st to end	Day	31% 6% 18% 28% 15% 2	4445
September	1st to 10th	Day	33% 6% 13% 30% 18% 1	2280
	11th to 20th	Day	32% 6% 17% 30% 14% 1	2120
	21st to end	Day	34% 6% 11% 31% 16% 1	2081
October	1st to 10th	Day	28% 4 8% 30% 29% 1	3160
	11th to 20th	Day	38% 4 13% 23% 20% 2	3140
	21st to end	Day	40% 4 14% 28% 13% 1	3412
November	1st to 10th	Day	41% 5% 15% 20% 16% 4	1681
	11th to 20th	Day	50% 6% 12% 21% 11% 1	1600
	21st to end	Day	47% 5% 16% 19% 11% 1	1600
December	1st to 10th	Day	51% 6% 16% 20% 7% 1	2610
	11th to 20th	Day	62% 5% 14% 14% 5%	3005
	21st to end	Day	65% 5% 11% 12% 6% 1	3982
January	1st to 10th	Night	62% 6% 9% 16% 6%	6348
	11th to 20th	Night	56% 5% 14% 13% 11% 1	5928
	21st to end	Night	48% 6% 12% 20% 14%	6490
February	1st to 10th	Night	50% 6% 12% 20% 9% 2	2600
	11th to 20th	Night	44% 7% 13% 21% 13% 2	2534
	21st to end	Night	44% 7% 13% 21% 12% 3	2084
March	1st to 10th	Night	37% 5% 11% 30% 16% 1	3546
	11th to 20th	Night	36% 7% 12% 29% 15% 1	3497
	21st to end	Night	62% 5% 12% 14% 6% 1	3817
April	1st to 10th	Night	43% 8% 13% 24% 11% 1	1964
	11th to 20th	Night	45% 6% 10% 21% 17% 2	1766
	21st to end	Night	43% 7% 10% 25% 13% 2	1710
May	1st to 10th	Night	39% 7% 13% 20% 20% 2	2850
	11th to 20th	Night	32% 8% 11% 26% 18% 5%	2584
	21st to end	Night	38% 7% 12% 25% 15% 2	2751
June	1st to 10th	Night	27% 8% 18% 27% 17% 3	1520
	11th to 20th	Night	31% 9% 16% 22% 19% 3	1361
	21st to end	Night	24% 7% 17% 32% 19% 2	1330
July	1st to 10th	Night	31% 7% 22% 24% 13% 2	2185
	11th to 20th	Night	18% 6% 14% 36% 22% 3	2465
	21st to end	Night	21% 8% 17% 32% 20% 2	2999
August	1st to 10th	Night	34% 5% 14% 27% 17% 3	2826
	11th to 20th	Night	32% 6% 15% 33% 12% 1	2825
	21st to end	Night	29% 7% 18% 27% 17% 2	3217
September	1st to 10th	Night	26% 4 14% 32% 22% 2	1900
	11th to 20th	Night	28% 6% 15% 33% 17% 2	2057
	21st to end	Night	29% 6% 12% 30% 22% 2	2090
October	1st to 10th	Night	23% 3 7% 28% 35% 4	3790
	11th to 20th	Night	27% 3 13% 30% 23% 3	3779
	21st to end	Night	41% 4 12% 28% 14% 1	4133
November	1st to 10th	Night	39% 5% 14% 21% 17% 3	2615
	11th to 20th	Night	45% 6% 12% 22% 13% 2	2800
	21st to end	Night	44% 6% 16% 22% 11% 1	2800
December	1st to 10th	Night	48% 5% 16% 23% 8%	4580
	11th to 20th	Night	55% 6% 16% 19% 4	5201
	21st to end	Night	63% 6% 10% 16% 4	6996

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	14% 12% 39% 22% 11% 2	300
	11th to 20th	Day	19% 14% 37% 25% 4 1	300
	21st to end	Day	12% 14% 38% 25% 9% 1	330
February	1st to 10th	Day	16% 16% 44% 21% 3	300
	11th to 20th	Day	13% 16% 40% 25% 4 1	300
	21st to end	Day	18% 16% 44% 19% 2	249
March	1st to 10th	Day	20% 14% 42% 21% 3	300
	11th to 20th	Day	22% 11% 37% 22% 8% 1	273
	21st to end	Day	27% 14% 29% 21% 7% 1	297
April	1st to 10th	Day	26% 16% 34% 18% 6%	395
	11th to 20th	Day	26% 15% 31% 21% 6% 1	559
	21st to end	Day	26% 16% 27% 20% 9% 2	650
May	1st to 10th	Day	21% 14% 32% 23% 8% 2	653
	11th to 20th	Day	21% 11% 30% 24% 12% 3	675
	21st to end	Day	17% 10% 29% 29% 13% 2	734
June	1st to 10th	Day	10% 8% 27% 31% 20% 5%	680
	11th to 20th	Day	15% 8% 35% 28% 11% 3	680
	21st to end	Day	10% 9% 32% 32% 15% 2	680
July	1st to 10th	Day	7% 6% 23% 33% 26% 6%	671
	11th to 20th	Day	7% 4 32% 31% 20% 7%	668
	21st to end	Day	6% 3 25% 40% 20% 5%	739
August	1st to 10th	Day	11% 5% 21% 37% 22% 5%	676
	11th to 20th	Day	13% 4 24% 33% 22% 5%	665
	21st to end	Day	8% 5% 30% 34% 18% 5%	701
September	1st to 10th	Day	15% 6% 29% 28% 19% 3	490
	11th to 20th	Day	9% 6% 34% 34% 14% 3	330
	21st to end	Day	16% 13% 32% 20% 14% 5%	300
October	1st to 10th	Day	20% 10% 31% 22% 13% 4	300
	11th to 20th	Day	15% 17% 41% 20% 7% 1	300
	21st to end	Day	22% 17% 37% 19% 5%	330
November	1st to 10th	Day	22% 13% 34% 22% 5% 3	300
	11th to 20th	Day	16% 23% 40% 17% 4	300
	21st to end	Day	19% 16% 40% 20% 5%	300
December	1st to 10th	Day	14% 12% 44% 21% 8%	300
	11th to 20th	Day	15% 15% 42% 22% 6%	300
	21st to end	Day	25% 16% 37% 20% 2	330
January	1st to 10th	Night	11% 12% 45% 24% 7% 1	1000
	11th to 20th	Night	12% 14% 41% 26% 6% 1	1000
	21st to end	Night	16% 14% 39% 26% 5%	1100
February	1st to 10th	Night	14% 13% 44% 24% 5% 1	1000
	11th to 20th	Night	13% 16% 42% 23% 6%	979
	21st to end	Night	13% 13% 41% 23% 7% 1	764
March	1st to 10th	Night	14% 12% 43% 24% 7%	617
	11th to 20th	Night	17% 13% 40% 25% 6%	575
	21st to end	Night	24% 11% 28% 27% 9% 1	627
April	1st to 10th	Night	20% 13% 40% 23% 4	570
	11th to 20th	Night	21% 13% 35% 24% 7% 1	563
	21st to end	Night	20% 12% 34% 25% 8% 1	570
May	1st to 10th	Night	17% 10% 36% 29% 7%	570
	11th to 20th	Night	18% 8% 33% 30% 9% 1	561
	21st to end	Night	17% 8% 30% 33% 11%	617
June	1st to 10th	Night	9% 6% 29% 42% 14% 1	570
	11th to 20th	Night	11% 5% 34% 40% 10%	570
	21st to end	Night	9% 4 26% 48% 13%	570
July	1st to 10th	Night	6% 2 26% 39% 26% 1	555
	11th to 20th	Night	2 2 29% 43% 22% 1	552
	21st to end	Night	4 1 25% 48% 20% 2	624
August	1st to 10th	Night	8% 2 21% 45% 21% 1	567
	11th to 20th	Night	8% 4 23% 41% 21% 3	564
	21st to end	Night	8% 3 27% 40% 19% 2	627
September	1st to 10th	Night	10% 4 28% 42% 15% 2	570
	11th to 20th	Night	10% 5% 34% 37% 13% 2	570
	21st to end	Night	11% 11% 33% 31% 13% 1	570
October	1st to 10th	Night	17% 9% 32% 31% 10% 1	750
	11th to 20th	Night	16% 14% 37% 26% 7%	760
	21st to end	Night	21% 13% 33% 26% 7%	837
November	1st to 10th	Night	15% 13% 37% 26% 8%	975
	11th to 20th	Night	15% 15% 41% 23% 6% 1	1000
	21st to end	Night	16% 14% 41% 24% 6%	1000
December	1st to 10th	Night	13% 13% 42% 26% 6%	1000
	11th to 20th	Night	18% 12% 38% 25% 6% 1	1000
	21st to end	Night	22% 14% 37% 23% 4	1100

Page generated at 2025-03-09 07:08:43. Version ac07

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