Stampede
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Stampede clear sky chart from 2005-11-06 to 2024-11-05.

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% 12% 5% 11% 7% 6% 6% 5% 6% 7% 24%	107412
	Night	6% 11% 5% 13% 8% 6% 6% 5% 6% 7% 27%	100249
Transparency	Day	55% 12% 14% 13% 4 1	107086
	Night	51% 11% 13% 15% 8% 3	100222
Seeing	Day	18% 12% 22% 25% 17% 5%	18539
	Night	13% 10% 20% 28% 23% 7%	22527

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	2 9% 3 9% 7% 7% 7% 4 7% 7% 39%	1269
	11th to 20th	Day	1 9% 5% 9% 6% 6% 7% 5% 7% 10% 36%	1258
	21st to end	Day	2 7% 4 11% 8% 8% 8% 6% 9% 8% 31%	1889
February	1st to 10th	Day	1 10% 5% 8% 5% 6% 6% 5% 6% 8% 40%	1185
	11th to 20th	Day	2 11% 5% 14% 7% 7% 5% 5% 9% 7% 28%	1417
	21st to end	Day	2 10% 7% 15% 9% 6% 7% 4 7% 6% 28%	1294
March	1st to 10th	Day	1 10% 8% 21% 10% 6% 6% 4 5% 5% 24%	3039
	11th to 20th	Day	2 10% 5% 13% 10% 10% 9% 6% 6% 6% 22%	3252
	21st to end	Day	2 11% 6% 13% 7% 6% 7% 5% 7% 8% 27%	4165
April	1st to 10th	Day	3 14% 7% 12% 7% 7% 6% 5% 7% 7% 26%	2405
	11th to 20th	Day	3 11% 6% 12% 8% 5% 6% 4 7% 7% 32%	2626
	21st to end	Day	5% 9% 3 8% 7% 6% 7% 5% 7% 8% 36%	2834
May	1st to 10th	Day	7% 13% 4 11% 7% 6% 7% 6% 8% 8% 24%	5070
	11th to 20th	Day	6% 11% 4 9% 6% 6% 6% 5% 7% 7% 33%	5398
	21st to end	Day	12% 13% 4 10% 6% 6% 5% 4 6% 8% 26%	6205
June	1st to 10th	Day	17% 11% 4 10% 7% 8% 8% 6% 8% 7% 16%	3566
	11th to 20th	Day	19% 11% 4 11% 7% 6% 6% 5% 6% 6% 21%	3800
	21st to end	Day	19% 10% 4 9% 8% 6% 7% 5% 7% 7% 20%	3800
July	1st to 10th	Day	26% 14% 4 9% 6% 5% 5% 3 5% 6% 17%	5993
	11th to 20th	Day	20% 9% 3 9% 7% 6% 6% 4 6% 8% 21%	5700
	21st to end	Day	21% 12% 4 9% 6% 5% 5% 4 5% 6% 24%	5969
August	1st to 10th	Day	23% 15% 4 11% 6% 6% 5% 4 5% 6% 16%	5046
	11th to 20th	Day	20% 13% 4 11% 6% 6% 6% 5% 7% 7% 15%	4705
	21st to end	Day	20% 15% 5% 13% 7% 6% 5% 4 5% 5% 15%	4884
September	1st to 10th	Day	19% 13% 4 10% 6% 6% 6% 4 5% 6% 21%	2433
	11th to 20th	Day	20% 14% 4 9% 6% 6% 6% 4 5% 6% 19%	2278
	21st to end	Day	15% 20% 5% 10% 6% 5% 3 4 5% 6% 21%	2024
October	1st to 10th	Day	8% 18% 6% 12% 5% 4 4 4 5% 6% 28%	3067
	11th to 20th	Day	4 12% 5% 18% 9% 7% 5% 4 5% 8% 24%	2740
	21st to end	Day	5% 19% 6% 12% 7% 7% 6% 4 6% 6% 22%	2539
November	1st to 10th	Day	4 17% 5% 13% 8% 8% 5% 4 4 6% 26%	1234
	11th to 20th	Day	5% 11% 6% 14% 10% 7% 6% 3 4 5% 27%	988
	21st to end	Day	4 11% 6% 12% 6% 8% 5% 5% 8% 8% 26%	822
December	1st to 10th	Day	3 11% 5% 12% 11% 7% 7% 7% 8% 9% 22%	675
	11th to 20th	Day	2 11% 5% 17% 10% 5% 5% 5% 7% 9% 25%	724
	21st to end	Day	1 6% 3 9% 7% 6% 7% 5% 9% 7% 39%	1119
January	1st to 10th	Night	1 7% 4 13% 7% 6% 5% 4 6% 8% 40%	5686
	11th to 20th	Night	2 9% 4 12% 8% 6% 6% 5% 5% 8% 36%	5650
	21st to end	Night	1 7% 3 10% 8% 8% 7% 5% 7% 8% 34%	5779
February	1st to 10th	Night	2 8% 4 12% 8% 5% 6% 4 6% 6% 39%	2993
	11th to 20th	Night	2 8% 4 13% 8% 7% 8% 5% 8% 11% 27%	2650
	21st to end	Night	2 11% 6% 17% 10% 6% 6% 4 5% 5% 27%	2158
March	1st to 10th	Night	1 10% 8% 19% 8% 6% 6% 5% 7% 5% 26%	3815
	11th to 20th	Night	1 8% 5% 14% 10% 11% 10% 6% 6% 6% 22%	3703
	21st to end	Night	2 11% 4 9% 6% 5% 6% 5% 8% 9% 33%	3466
April	1st to 10th	Night	3 15% 6% 12% 7% 5% 6% 5% 9% 8% 24%	1772
	11th to 20th	Night	3 12% 4 11% 6% 4 5% 5% 7% 9% 35%	1503
	21st to end	Night	5% 8% 4 7% 5% 5% 5% 5% 8% 10% 39%	1344
May	1st to 10th	Night	4 12% 4 12% 7% 7% 7% 6% 9% 9% 22%	1900
	11th to 20th	Night	7% 9% 3 9% 6% 7% 7% 4 8% 6% 33%	1502
	21st to end	Night	12% 10% 3 8% 6% 5% 5% 6% 6% 7% 31%	1381
June	1st to 10th	Night	13% 13% 3 9% 8% 8% 7% 5% 8% 7% 19%	613
	11th to 20th	Night	19% 11% 4 8% 7% 5% 4 4 5% 7% 26%	380
	21st to end	Night	19% 8% 2 9% 6% 7% 6% 5% 7% 9% 22%	380
July	1st to 10th	Night	21% 16% 4 10% 6% 6% 5% 4 5% 6% 17%	974
	11th to 20th	Night	17% 13% 4 11% 6% 5% 6% 3 7% 7% 22%	1270
	21st to end	Night	21% 13% 5% 12% 6% 4 4 3 6% 6% 20%	1596
August	1st to 10th	Night	23% 14% 4 9% 6% 5% 6% 4 6% 5% 16%	1894
	11th to 20th	Night	17% 11% 5% 13% 8% 7% 6% 5% 6% 7% 16%	2131
	21st to end	Night	20% 17% 5% 11% 6% 5% 5% 4 5% 5% 16%	2783
September	1st to 10th	Night	19% 11% 3 9% 7% 6% 5% 4 7% 6% 23%	1744
	11th to 20th	Night	21% 14% 5% 10% 6% 5% 5% 3 5% 7% 19%	1902
	21st to end	Night	16% 20% 5% 10% 6% 5% 5% 3 5% 5% 20%	2154
October	1st to 10th	Night	7% 17% 5% 11% 6% 5% 6% 5% 6% 8% 23%	3896
	11th to 20th	Night	5% 16% 7% 17% 8% 6% 5% 4 6% 7% 20%	4188
	21st to end	Night	5% 15% 5% 15% 9% 7% 6% 3 5% 7% 23%	5020
November	1st to 10th	Night	4 15% 6% 14% 7% 5% 5% 3 5% 6% 28%	2943
	11th to 20th	Night	4 13% 7% 15% 11% 8% 6% 4 4 5% 24%	3191
	21st to end	Night	3 10% 5% 12% 8% 7% 6% 5% 7% 7% 29%	3357
December	1st to 10th	Night	3 10% 4 12% 9% 7% 7% 5% 7% 8% 27%	3485
	11th to 20th	Night	2 11% 7% 15% 8% 7% 6% 5% 7% 7% 26%	4470
	21st to end	Night	2 6% 4 13% 9% 7% 6% 6% 7% 7% 33%	6576

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	39% 11% 14% 21% 10% 4	1269
	11th to 20th	Day	38% 12% 17% 20% 7% 6%	1270
	21st to end	Day	43% 7% 11% 11% 16% 11%	1889
February	1st to 10th	Day	39% 8% 11% 18% 16% 8%	1185
	11th to 20th	Day	49% 12% 14% 13% 8% 2	1423
	21st to end	Day	53% 9% 10% 15% 12% 2	1294
March	1st to 10th	Day	58% 8% 9% 10% 14% 2	3039
	11th to 20th	Day	51% 13% 13% 14% 8% 2	3252
	21st to end	Day	47% 16% 16% 11% 7% 2	4165
April	1st to 10th	Day	55% 11% 13% 14% 7%	2405
	11th to 20th	Day	49% 11% 14% 15% 8% 2	2626
	21st to end	Day	43% 10% 15% 21% 10%	2834
May	1st to 10th	Day	49% 15% 18% 15% 3	5070
	11th to 20th	Day	42% 15% 15% 23% 5%	5401
	21st to end	Day	50% 14% 15% 16% 4	6206
June	1st to 10th	Day	60% 16% 14% 9% 1	3566
	11th to 20th	Day	61% 12% 13% 11% 3	3800
	21st to end	Day	60% 14% 16% 9%	3800
July	1st to 10th	Day	66% 11% 16% 7% 1	5903
	11th to 20th	Day	57% 10% 14% 19% 1	5601
	21st to end	Day	58% 11% 15% 13% 2	5780
August	1st to 10th	Day	68% 9% 15% 8% 1	5027
	11th to 20th	Day	62% 13% 15% 9% 1	4753
	21st to end	Day	67% 12% 12% 9% 1	4883
September	1st to 10th	Day	63% 12% 13% 10% 1	2433
	11th to 20th	Day	63% 13% 14% 10%	2278
	21st to end	Day	63% 10% 11% 14% 2	2024
October	1st to 10th	Day	56% 8% 9% 19% 6% 1	3067
	11th to 20th	Day	56% 11% 15% 15% 3 1	2740
	21st to end	Day	60% 10% 12% 15% 2 1	2539
November	1st to 10th	Day	58% 10% 11% 14% 5% 3	1234
	11th to 20th	Day	58% 7% 13% 15% 6% 1	988
	21st to end	Day	51% 10% 18% 13% 8% 1	822
December	1st to 10th	Day	55% 10% 12% 11% 10% 2	675
	11th to 20th	Day	52% 9% 14% 16% 7% 2	726
	21st to end	Day	34% 10% 16% 14% 18% 7%	1119
January	1st to 10th	Night	38% 10% 15% 25% 7% 4	5686
	11th to 20th	Night	40% 13% 16% 20% 8% 3	5700
	21st to end	Night	41% 9% 10% 10% 18% 13%	5779
February	1st to 10th	Night	43% 7% 9% 16% 16% 8%	2993
	11th to 20th	Night	46% 11% 14% 15% 11% 3	2655
	21st to end	Night	56% 7% 9% 15% 10% 2	2158
March	1st to 10th	Night	56% 6% 10% 9% 16% 4	3815
	11th to 20th	Night	50% 13% 14% 13% 8% 2	3705
	21st to end	Night	38% 15% 16% 16% 11% 3	3466
April	1st to 10th	Night	52% 10% 13% 17% 7% 1	1772
	11th to 20th	Night	42% 12% 18% 17% 8% 2	1503
	21st to end	Night	35% 12% 14% 27% 11%	1344
May	1st to 10th	Night	50% 15% 18% 15% 2	1900
	11th to 20th	Night	41% 14% 16% 23% 7%	1502
	21st to end	Night	45% 14% 17% 19% 5%	1381
June	1st to 10th	Night	58% 15% 13% 12% 1	613
	11th to 20th	Night	57% 11% 15% 15% 2	380
	21st to end	Night	57% 16% 19% 8%	380
July	1st to 10th	Night	67% 9% 17% 6% 1	955
	11th to 20th	Night	58% 9% 13% 20%	1246
	21st to end	Night	62% 10% 15% 11% 2	1546
August	1st to 10th	Night	66% 12% 18% 4 1	1888
	11th to 20th	Night	61% 14% 16% 8%	2149
	21st to end	Night	67% 12% 15% 6%	2783
September	1st to 10th	Night	60% 13% 15% 11% 1	1744
	11th to 20th	Night	65% 9% 13% 12% 1	1902
	21st to end	Night	65% 10% 10% 13% 2	2154
October	1st to 10th	Night	56% 9% 12% 18% 4	3896
	11th to 20th	Night	61% 10% 11% 14% 3 1	4188
	21st to end	Night	57% 10% 13% 17% 3 1	5020
November	1st to 10th	Night	55% 9% 12% 17% 5% 2	2943
	11th to 20th	Night	61% 8% 12% 13% 6%	3191
	21st to end	Night	50% 9% 14% 17% 8% 2	3357
December	1st to 10th	Night	52% 10% 12% 14% 9% 2	3485
	11th to 20th	Night	52% 12% 13% 13% 10% 1	4467
	21st to end	Night	40% 12% 14% 12% 15% 6%	6576

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	7% 10% 20% 31% 19% 13%	90
	11th to 20th	Day	2 2 34% 34% 18% 9%	90
	21st to end	Day	7% 11% 20% 32% 24% 6%	293
February	1st to 10th	Day	4 9% 24% 25% 24% 13%	280
	11th to 20th	Day	10% 19% 23% 24% 16% 8%	335
	21st to end	Day	9% 17% 30% 27% 14% 4	307
March	1st to 10th	Day	6% 13% 27% 30% 20% 4	370
	11th to 20th	Day	6% 10% 24% 33% 23% 4	409
	21st to end	Day	8% 13% 27% 30% 17% 5%	616
April	1st to 10th	Day	7% 16% 32% 24% 17% 4	596
	11th to 20th	Day	9% 12% 23% 30% 20% 5%	640
	21st to end	Day	10% 7% 22% 32% 25% 4	650
May	1st to 10th	Day	12% 12% 26% 30% 16% 3	653
	11th to 20th	Day	12% 13% 26% 28% 17% 5%	736
	21st to end	Day	19% 14% 23% 24% 16% 5%	940
June	1st to 10th	Day	18% 10% 22% 26% 19% 6%	993
	11th to 20th	Day	19% 8% 20% 25% 21% 7%	1060
	21st to end	Day	19% 8% 18% 24% 21% 9%	1060
July	1st to 10th	Day	22% 12% 22% 24% 16% 4	933
	11th to 20th	Day	30% 11% 19% 22% 14% 4	852
	21st to end	Day	24% 11% 20% 25% 15% 6%	908
August	1st to 10th	Day	29% 16% 24% 16% 11% 4	676
	11th to 20th	Day	31% 15% 21% 21% 10% 2	665
	21st to end	Day	33% 15% 20% 21% 10% 1	748
September	1st to 10th	Day	28% 15% 23% 18% 12% 4	633
	11th to 20th	Day	33% 19% 21% 16% 8% 2	578
	21st to end	Day	26% 11% 19% 20% 17% 7%	390
October	1st to 10th	Day	25% 17% 23% 17% 12% 5%	390
	11th to 20th	Day	10% 8% 22% 27% 21% 11%	390
	21st to end	Day	14% 10% 19% 26% 22% 8%	429
November	1st to 10th	Day	11% 10% 19% 28% 21% 11%	332
	11th to 20th	Day	9% 13% 21% 25% 25% 7%	128
	21st to end	Day	10% 13% 18% 29% 21% 9%	90
December	1st to 10th	Day	9% 11% 28% 23% 23% 6%	90
	11th to 20th	Day	9% 11% 20% 31% 22% 7%	90
	21st to end	Day	10% 15% 18% 39% 11% 6%	99
January	1st to 10th	Night	6% 8% 19% 30% 27% 10%	940
	11th to 20th	Night	8% 6% 24% 35% 21% 6%	940
	21st to end	Night	7% 9% 22% 35% 23% 5%	983
February	1st to 10th	Night	6% 8% 24% 28% 24% 9%	850
	11th to 20th	Night	8% 15% 24% 30% 19% 4	834
	21st to end	Night	10% 15% 22% 29% 22% 2	663
March	1st to 10th	Night	6% 11% 21% 38% 21% 4	660
	11th to 20th	Night	5% 5% 19% 31% 31% 8%	659
	21st to end	Night	7% 11% 19% 25% 27% 11%	627
April	1st to 10th	Night	9% 11% 25% 28% 20% 6%	570
	11th to 20th	Night	8% 10% 18% 28% 28% 8%	563
	21st to end	Night	9% 5% 14% 32% 33% 7%	518
May	1st to 10th	Night	10% 9% 17% 27% 31% 7%	380
	11th to 20th	Night	10% 12% 20% 30% 25% 3	220
	21st to end	Night	13% 11% 21% 26% 25% 4	206
June	1st to 10th	Night	16% 11% 18% 28% 25% 2	190
	11th to 20th	Night	23% 7% 13% 25% 27% 5%	190
	21st to end	Night	20% 7% 12% 22% 34% 5%	190
July	1st to 10th	Night	23% 9% 18% 22% 24% 5%	185
	11th to 20th	Night	32% 9% 18% 21% 17% 3	184
	21st to end	Night	27% 7% 20% 21% 20% 4	289
August	1st to 10th	Night	31% 14% 15% 20% 16% 3	378
	11th to 20th	Night	28% 11% 22% 21% 15% 3	444
	21st to end	Night	30% 11% 14% 19% 20% 6%	627
September	1st to 10th	Night	26% 13% 22% 17% 17% 5%	570
	11th to 20th	Night	30% 16% 17% 17% 14% 6%	570
	21st to end	Night	26% 10% 12% 26% 20% 6%	605
October	1st to 10th	Night	24% 15% 17% 20% 18% 5%	727
	11th to 20th	Night	15% 10% 17% 26% 25% 8%	860
	21st to end	Night	13% 10% 17% 32% 22% 6%	946
November	1st to 10th	Night	10% 9% 19% 31% 24% 6%	854
	11th to 20th	Night	12% 7% 19% 32% 22% 8%	850
	21st to end	Night	9% 10% 21% 27% 26% 7%	910
December	1st to 10th	Night	9% 15% 22% 26% 21% 8%	1005
	11th to 20th	Night	9% 9% 21% 29% 23% 8%	1130
	21st to end	Night	8% 12% 17% 30% 22% 9%	1210

Page generated at 2024-11-02 22:11:12. Version ac07

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