Prairie Peak
Clear Sky Chart
History

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

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	17% 9% 3 7% 4 4 4 3 5% 6% 38%	101486
	Night	19% 10% 3 7% 4 4 4 3 4 5% 36%	97624
Transparency	Day	47% 6% 11% 17% 13% 5%	101234
	Night	50% 6% 11% 17% 11% 5%	97465
Seeing	Day	25% 12% 24% 25% 13% 3	14786
	Night	26% 6% 15% 30% 20% 2	23706

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	32% 18% 5% 12% 7% 5% 4 3 3 3 8%	2539
	11th to 20th	Day	37% 13% 5% 9% 4 4 3 2 3 4 17%	2613
	21st to end	Day	34% 13% 4 9% 6% 5% 4 4 4 5% 13%	3146
February	1st to 10th	Day	29% 15% 4 9% 6% 5% 5% 4 4 5% 14%	1710
	11th to 20th	Day	27% 15% 5% 10% 5% 4 4 4 5% 5% 16%	1665
	21st to end	Day	27% 19% 5% 9% 5% 4 3 4 4 3 17%	1465
March	1st to 10th	Day	21% 20% 5% 9% 5% 5% 5% 3 5% 5% 18%	3384
	11th to 20th	Day	20% 13% 3 8% 5% 3 3 2 4 4 36%	3490
	21st to end	Day	25% 16% 5% 11% 7% 5% 5% 4 4 4 13%	3841
April	1st to 10th	Day	27% 17% 5% 10% 6% 4 4 3 4 4 16%	2280
	11th to 20th	Day	25% 15% 4 8% 6% 4 4 3 4 5% 22%	2263
	21st to end	Day	21% 12% 4 9% 7% 4 5% 3 6% 7% 23%	2470
May	1st to 10th	Day	18% 10% 4 9% 5% 4 4 4 5% 6% 32%	4217
	11th to 20th	Day	11% 6% 2 5% 3 2 3 3 6% 7% 51%	4377
	21st to end	Day	15% 8% 3 7% 5% 6% 7% 5% 8% 7% 28%	4813
June	1st to 10th	Day	21% 10% 3 7% 5% 4 4 3 5% 6% 32%	2660
	11th to 20th	Day	14% 10% 3 8% 5% 5% 6% 4 7% 8% 31%	2660
	21st to end	Day	8% 5% 2 5% 4 3 4 3 6% 7% 53%	2660
July	1st to 10th	Day	3 2 1 3 2 2 2 2 4 5% 75%	4420
	11th to 20th	Day	4 3 1 3 2 2 2 2 3 5% 73%	4420
	21st to end	Day	3 3 1 2 2 2 2 2 3 5% 76%	4643
August	1st to 10th	Day	2 3 1 3 3 3 3 3 4 7% 68%	4091
	11th to 20th	Day	5% 4 2 4 3 4 5% 4 7% 8% 54%	4026
	21st to end	Day	7% 4 1 4 3 4 4 4 5% 7% 57%	4335
September	1st to 10th	Day	5% 3 1 3 3 2 3 3 5% 7% 65%	2280
	11th to 20th	Day	10% 6% 2 7% 4 4 4 4 6% 8% 45%	2226
	21st to end	Day	14% 7% 2 6% 4 3 4 3 4 6% 46%	2030
October	1st to 10th	Day	15% 9% 3 7% 5% 4 3 3 5% 5% 42%	1900
	11th to 20th	Day	18% 8% 3 7% 5% 6% 4 4 4 6% 34%	1900
	21st to end	Day	22% 11% 4 8% 4 4 5% 3 5% 6% 27%	2090
November	1st to 10th	Day	29% 10% 6% 10% 5% 4 4 3 5% 6% 17%	1590
	11th to 20th	Day	30% 11% 4 8% 5% 6% 5% 4 5% 6% 18%	1520
	21st to end	Day	26% 11% 4 9% 6% 4 4 4 5% 6% 21%	1520
December	1st to 10th	Day	27% 11% 4 10% 6% 3 3 4 4 6% 24%	1520
	11th to 20th	Day	28% 13% 4 11% 5% 5% 5% 3 6% 6% 13%	1928
	21st to end	Day	31% 17% 4 13% 6% 5% 4 3 4 4 9%	2794
January	1st to 10th	Night	33% 17% 5% 13% 7% 5% 3 2 2 3 9%	4406
	11th to 20th	Night	35% 16% 5% 10% 4 3 3 2 3 3 16%	4346
	21st to end	Night	39% 15% 4 8% 4 3 2 2 3 4 15%	4521
February	1st to 10th	Night	24% 16% 4 10% 6% 4 4 4 5% 5% 17%	2470
	11th to 20th	Night	23% 14% 4 8% 6% 5% 3 3 4 5% 25%	2402
	21st to end	Night	24% 16% 4 9% 5% 5% 4 3 4 4 20%	1988
March	1st to 10th	Night	19% 20% 5% 10% 5% 4 4 3 5% 6% 21%	3475
	11th to 20th	Night	17% 10% 3 7% 4 4 4 3 4 5% 40%	3490
	21st to end	Night	22% 19% 4 12% 6% 5% 4 3 4 4 17%	3811
April	1st to 10th	Night	23% 14% 4 10% 5% 5% 4 2 5% 5% 22%	1900
	11th to 20th	Night	18% 12% 4 8% 4 3 4 5% 5% 6% 30%	1860
	21st to end	Night	19% 9% 3 8% 6% 5% 5% 4 5% 7% 31%	1710
May	1st to 10th	Night	20% 8% 3 7% 4 3 3 3 4 4 40%	2746
	11th to 20th	Night	8% 5% 2 5% 4 3 3 3 4 6% 56%	2516
	21st to end	Night	10% 9% 3 7% 4 5% 5% 4 7% 8% 40%	2762
June	1st to 10th	Night	16% 9% 3 4 4 5% 3 4 6% 6% 39%	1520
	11th to 20th	Night	10% 5% 3 6% 4 3 3 5% 6% 8% 47%	1520
	21st to end	Night	7% 4 2 4 3 3 3 3 4 6% 61%	1520
July	1st to 10th	Night	1 2 1 2 1 1 1 1 2 5% 82%	2540
	11th to 20th	Night	3 3 1 2 2 1 2 2 4 6% 75%	2540
	21st to end	Night	2 2 1 2 2 2 2 2 3 5% 77%	2910
August	1st to 10th	Night	1 2 1 2 2 2 3 3 6% 8% 72%	2848
	11th to 20th	Night	3 2 1 4 4 4 4 4 6% 9% 59%	2812
	21st to end	Night	4 4 1 5% 2 3 3 2 4 6% 65%	3338
September	1st to 10th	Night	5% 3 1 3 2 2 2 2 4 6% 68%	1900
	11th to 20th	Night	8% 5% 2 5% 4 3 4 3 5% 7% 54%	1951
	21st to end	Night	10% 6% 2 5% 3 3 3 3 5% 7% 53%	2149
October	1st to 10th	Night	12% 7% 2 6% 3 4 4 3 4 6% 49%	2280
	11th to 20th	Night	16% 7% 3 6% 4 4 4 3 6% 7% 40%	2280
	21st to end	Night	22% 8% 3 9% 3 4 4 3 4 5% 34%	2508
November	1st to 10th	Night	27% 11% 3 8% 5% 4 5% 3 4 6% 25%	2487
	11th to 20th	Night	30% 11% 3 10% 5% 5% 4 3 4 5% 20%	2660
	21st to end	Night	21% 10% 3 8% 5% 6% 5% 4 5% 5% 28%	2660
December	1st to 10th	Night	25% 11% 3 7% 5% 5% 4 4 5% 5% 26%	2660
	11th to 20th	Night	29% 13% 4 10% 5% 5% 4 3 4 6% 18%	3276
	21st to end	Night	27% 15% 5% 12% 8% 5% 5% 3 4 4 13%	4862

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	81% 7% 5% 4 2 1	2539
	11th to 20th	Day	73% 5% 6% 8% 4 4	2613
	21st to end	Day	73% 7% 7% 7% 6% 1	3146
February	1st to 10th	Day	72% 6% 7% 9% 5%	1710
	11th to 20th	Day	68% 7% 10% 7% 5% 2	1674
	21st to end	Day	73% 4 8% 9% 5% 2	1465
March	1st to 10th	Day	67% 7% 10% 13% 4	3384
	11th to 20th	Day	53% 4 7% 23% 11% 1	3490
	21st to end	Day	73% 8% 8% 7% 4	3841
April	1st to 10th	Day	72% 5% 10% 9% 4	2280
	11th to 20th	Day	65% 6% 9% 11% 6% 2	2266
	21st to end	Day	60% 7% 11% 15% 6% 1	2470
May	1st to 10th	Day	52% 7% 12% 17% 12%	4217
	11th to 20th	Day	32% 5% 16% 31% 15% 1	4380
	21st to end	Day	49% 11% 24% 15% 2	4814
June	1st to 10th	Day	53% 6% 14% 20% 6%	2660
	11th to 20th	Day	49% 8% 18% 18% 6%	2660
	21st to end	Day	31% 5% 17% 29% 14% 3	2660
July	1st to 10th	Day	15% 3 10% 14% 27% 31%	4351
	11th to 20th	Day	16% 2 6% 19% 33% 23%	4345
	21st to end	Day	13% 3 10% 27% 39% 9%	4496
August	1st to 10th	Day	17% 5% 9% 28% 29% 11%	4076
	11th to 20th	Day	25% 8% 15% 33% 15% 3	4065
	21st to end	Day	27% 5% 12% 25% 22% 8%	4334
September	1st to 10th	Day	21% 4 10% 32% 21% 13%	2280
	11th to 20th	Day	36% 8% 13% 21% 17% 6%	2226
	21st to end	Day	39% 6% 11% 23% 17% 5%	2030
October	1st to 10th	Day	44% 6% 9% 16% 20% 6%	1900
	11th to 20th	Day	50% 8% 9% 15% 15% 2	1900
	21st to end	Day	57% 7% 7% 13% 14% 2	2090
November	1st to 10th	Day	68% 6% 7% 13% 5%	1590
	11th to 20th	Day	66% 8% 9% 8% 6% 3	1520
	21st to end	Day	64% 6% 7% 7% 13% 3	1520
December	1st to 10th	Day	62% 6% 8% 11% 11% 1	1520
	11th to 20th	Day	69% 7% 11% 9% 2	1928
	21st to end	Day	77% 7% 7% 5% 3 1	2794
January	1st to 10th	Night	81% 5% 5% 4 3 1	4406
	11th to 20th	Night	75% 4 6% 9% 3 3	4346
	21st to end	Night	75% 3 6% 9% 6% 1	4521
February	1st to 10th	Night	69% 6% 9% 11% 4 1	2470
	11th to 20th	Night	63% 6% 11% 11% 8% 2	2404
	21st to end	Night	67% 5% 9% 11% 6% 2	1988
March	1st to 10th	Night	64% 6% 11% 14% 4	3475
	11th to 20th	Night	48% 7% 12% 22% 11% 1	3490
	21st to end	Night	69% 7% 11% 11% 1	3811
April	1st to 10th	Night	65% 6% 11% 12% 5%	1900
	11th to 20th	Night	54% 8% 14% 17% 4 3	1860
	21st to end	Night	54% 6% 13% 18% 7% 2	1710
May	1st to 10th	Night	47% 6% 13% 22% 10% 1	2746
	11th to 20th	Night	31% 4 15% 33% 14% 4	2516
	21st to end	Night	40% 10% 30% 17% 3	2762
June	1st to 10th	Night	45% 8% 14% 29% 4 1	1520
	11th to 20th	Night	34% 7% 22% 28% 8% 1	1520
	21st to end	Night	26% 5% 18% 32% 14% 4	1520
July	1st to 10th	Night	11% 3 11% 17% 24% 35%	2500
	11th to 20th	Night	15% 3 8% 18% 25% 32%	2492
	21st to end	Night	14% 3 10% 27% 37% 10%	2819
August	1st to 10th	Night	13% 5% 13% 27% 28% 13%	2839
	11th to 20th	Night	25% 8% 16% 33% 15% 5%	2839
	21st to end	Night	22% 5% 10% 31% 24% 8%	3338
September	1st to 10th	Night	20% 4 10% 28% 25% 13%	1900
	11th to 20th	Night	32% 5% 13% 25% 16% 9%	1951
	21st to end	Night	32% 5% 14% 23% 17% 9%	2149
October	1st to 10th	Night	38% 6% 8% 23% 18% 7%	2280
	11th to 20th	Night	44% 7% 11% 18% 16% 4	2280
	21st to end	Night	52% 6% 9% 14% 14% 5%	2508
November	1st to 10th	Night	61% 7% 8% 14% 9% 1	2487
	11th to 20th	Night	67% 6% 9% 9% 7% 3	2660
	21st to end	Night	57% 7% 10% 9% 12% 6%	2660
December	1st to 10th	Night	59% 7% 9% 12% 11% 1	2660
	11th to 20th	Night	69% 7% 9% 9% 5%	3276
	21st to end	Night	73% 9% 7% 7% 3 1	4862

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	46% 17% 18% 11% 8%	180
	11th to 20th	Day	44% 11% 19% 15% 10% 1	227
	21st to end	Day	40% 11% 17% 18% 11% 2	407
February	1st to 10th	Day	40% 14% 18% 20% 8% 1	370
	11th to 20th	Day	42% 15% 20% 17% 5% 1	365
	21st to end	Day	42% 15% 19% 17% 6% 1	332
March	1st to 10th	Day	41% 15% 20% 17% 7%	460
	11th to 20th	Day	35% 12% 23% 20% 9% 2	460
	21st to end	Day	41% 17% 19% 15% 7% 1	506
April	1st to 10th	Day	38% 16% 18% 18% 8% 2	460
	11th to 20th	Day	36% 18% 22% 16% 5% 3	452
	21st to end	Day	30% 17% 25% 19% 7% 2	460
May	1st to 10th	Day	22% 16% 30% 19% 10% 3	463
	11th to 20th	Day	30% 11% 21% 25% 9% 3	488
	21st to end	Day	22% 11% 24% 25% 16% 3	529
June	1st to 10th	Day	24% 10% 26% 24% 13% 2	490
	11th to 20th	Day	20% 19% 29% 22% 10% 1	490
	21st to end	Day	9% 9% 28% 37% 16% 2	490
July	1st to 10th	Day	7% 7% 32% 34% 17% 3	486
	11th to 20th	Day	5% 8% 30% 36% 17% 3	484
	21st to end	Day	4 5% 27% 40% 20% 4	531
August	1st to 10th	Day	3 4 30% 38% 20% 6%	487
	11th to 20th	Day	5% 5% 22% 34% 29% 6%	477
	21st to end	Day	8% 8% 28% 33% 18% 4	539
September	1st to 10th	Day	7% 8% 30% 32% 20% 3	490
	11th to 20th	Day	17% 8% 24% 31% 16% 4	490
	21st to end	Day	18% 13% 24% 32% 10% 4	490
October	1st to 10th	Day	20% 12% 26% 23% 15% 4	490
	11th to 20th	Day	22% 12% 20% 23% 18% 4	490
	21st to end	Day	32% 14% 21% 20% 9% 4	539
November	1st to 10th	Day	36% 13% 21% 20% 8% 2	246
	11th to 20th	Day	33% 13% 23% 20% 9% 2	180
	21st to end	Day	38% 14% 17% 17% 13% 1	180
December	1st to 10th	Day	38% 11% 17% 21% 8% 6%	180
	11th to 20th	Day	46% 7% 22% 16% 8% 1	180
	21st to end	Day	38% 16% 18% 19% 9% 1	198
January	1st to 10th	Night	46% 8% 14% 18% 11% 2	760
	11th to 20th	Night	39% 7% 14% 21% 16% 3	760
	21st to end	Night	36% 4 13% 29% 16% 2	836
February	1st to 10th	Night	35% 8% 13% 29% 14% 2	760
	11th to 20th	Night	33% 7% 16% 29% 14% 1	744
	21st to end	Night	38% 11% 14% 22% 14%	628
March	1st to 10th	Night	34% 9% 19% 26% 10% 1	760
	11th to 20th	Night	31% 9% 16% 27% 15% 2	760
	21st to end	Night	36% 10% 16% 24% 13% 1	836
April	1st to 10th	Night	34% 9% 16% 24% 16% 1	760
	11th to 20th	Night	26% 11% 21% 25% 15% 2	732
	21st to end	Night	23% 8% 20% 29% 19% 2	570
May	1st to 10th	Night	19% 5% 21% 33% 19% 2	508
	11th to 20th	Night	17% 5% 16% 36% 24% 2	374
	21st to end	Night	17% 4 18% 36% 22% 2	411
June	1st to 10th	Night	21% 4 16% 32% 26% 1	380
	11th to 20th	Night	14% 4 20% 43% 18% 2	380
	21st to end	Night	12% 2 14% 45% 27% 1	380
July	1st to 10th	Night	4 3 12% 48% 33%	370
	11th to 20th	Night	6% 2 13% 53% 24% 1	368
	21st to end	Night	3 2 10% 47% 37% 2	503
August	1st to 10th	Night	3 2 9% 44% 37% 6%	567
	11th to 20th	Night	5% 1 9% 38% 43% 5%	564
	21st to end	Night	7% 3 17% 40% 30% 3	741
September	1st to 10th	Night	7% 4 16% 40% 31% 2	760
	11th to 20th	Night	11% 3 16% 32% 32% 5%	760
	21st to end	Night	14% 5% 13% 39% 25% 3	760
October	1st to 10th	Night	16% 6% 18% 31% 25% 3	760
	11th to 20th	Night	23% 5% 12% 33% 24% 5%	760
	21st to end	Night	31% 7% 17% 24% 16% 4	836
November	1st to 10th	Night	34% 6% 14% 29% 16% 1	742
	11th to 20th	Night	37% 9% 17% 22% 14% 1	760
	21st to end	Night	26% 9% 17% 28% 17% 3	760
December	1st to 10th	Night	31% 6% 17% 26% 18% 3	760
	11th to 20th	Night	41% 7% 14% 22% 15% 1	760
	21st to end	Night	42% 11% 15% 23% 9% 1	836

Page generated at 2024-10-29 08:20:50. Version ac07

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