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 2024-04-25.

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% 11% 5% 10% 8% 5% 6% 6% 6% 7% 24%	81628
	Night	6% 10% 5% 11% 9% 5% 6% 6% 6% 7% 29%	87475
Transparency	Day	56% 12% 14% 12% 5% 1	81254
	Night	50% 11% 13% 14% 9% 3	87430
Seeing	Day	18% 12% 22% 25% 17% 5%	17572
	Night	13% 10% 20% 28% 23% 7%	22064

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 8% 3 9% 7% 6% 7% 6% 6% 8% 39%	1269
	11th to 20th	Day	1 8% 5% 8% 7% 4 7% 6% 7% 10% 36%	1258
	21st to end	Day	2 7% 4 10% 9% 5% 8% 7% 9% 8% 31%	1889
February	1st to 10th	Day	2 9% 6% 7% 6% 4 6% 7% 6% 9% 40%	1185
	11th to 20th	Day	2 10% 5% 13% 9% 4 7% 5% 9% 8% 28%	1417
	21st to end	Day	2 9% 7% 13% 10% 5% 7% 5% 7% 6% 28%	1294
March	1st to 10th	Day	1 9% 8% 18% 13% 5% 6% 5% 6% 5% 24%	3039
	11th to 20th	Day	2 10% 5% 11% 12% 7% 10% 9% 6% 6% 22%	3252
	21st to end	Day	2 10% 6% 11% 9% 5% 7% 7% 7% 8% 27%	4165
April	1st to 10th	Day	3 13% 7% 11% 7% 5% 7% 7% 6% 7% 26%	2405
	11th to 20th	Day	3 10% 7% 11% 8% 4 6% 5% 7% 7% 32%	2626
	21st to end	Day	5% 8% 4 8% 7% 4 7% 7% 7% 8% 35%	2746
May	1st to 10th	Day	7% 12% 4 8% 8% 4 6% 7% 7% 8% 29%	2880
	11th to 20th	Day	7% 12% 4 7% 6% 4 6% 6% 7% 8% 32%	3035
	21st to end	Day	13% 11% 4 7% 6% 4 6% 6% 7% 9% 27%	3499
June	1st to 10th	Day	18% 11% 5% 8% 8% 6% 8% 7% 8% 7% 16%	3377
	11th to 20th	Day	19% 10% 5% 10% 8% 4 6% 6% 6% 7% 21%	3600
	21st to end	Day	20% 9% 5% 8% 9% 5% 7% 6% 6% 6% 19%	3600
July	1st to 10th	Day	21% 8% 4 8% 8% 4 6% 5% 7% 7% 23%	3412
	11th to 20th	Day	28% 12% 4 9% 8% 4 5% 5% 5% 6% 13%	3240
	21st to end	Day	23% 10% 5% 8% 8% 5% 6% 6% 6% 7% 18%	3417
August	1st to 10th	Day	26% 12% 4 9% 8% 5% 4 5% 5% 6% 15%	2865
	11th to 20th	Day	26% 11% 4 8% 7% 5% 6% 6% 6% 6% 15%	2690
	21st to end	Day	25% 14% 5% 10% 7% 4 5% 5% 4 6% 14%	2772
September	1st to 10th	Day	20% 12% 4 8% 8% 4 6% 6% 5% 6% 21%	2306
	11th to 20th	Day	20% 13% 4 8% 7% 5% 6% 6% 5% 6% 20%	2159
	21st to end	Day	15% 19% 6% 9% 7% 4 4 5% 5% 6% 20%	1918
October	1st to 10th	Day	13% 17% 6% 10% 6% 4 5% 5% 6% 6% 22%	1746
	11th to 20th	Day	6% 14% 5% 13% 7% 3 6% 5% 5% 8% 27%	1566
	21st to end	Day	6% 14% 6% 9% 8% 4 7% 6% 7% 7% 26%	1468
November	1st to 10th	Day	4 16% 5% 10% 10% 6% 6% 6% 4 6% 27%	1205
	11th to 20th	Day	5% 11% 6% 12% 11% 6% 7% 5% 4 5% 28%	988
	21st to end	Day	5% 10% 6% 11% 8% 7% 5% 6% 8% 9% 27%	822
December	1st to 10th	Day	3 10% 6% 11% 11% 5% 6% 9% 8% 9% 22%	675
	11th to 20th	Day	2 10% 5% 15% 12% 4 5% 6% 6% 9% 25%	724
	21st to end	Day	1 6% 4 7% 8% 4 7% 7% 9% 7% 39%	1119
January	1st to 10th	Night	1 6% 4 11% 8% 4 5% 5% 6% 8% 40%	5686
	11th to 20th	Night	2 8% 5% 10% 9% 4 6% 6% 6% 8% 36%	5650
	21st to end	Night	1 6% 4 9% 9% 6% 8% 7% 7% 8% 34%	5779
February	1st to 10th	Night	2 7% 4 11% 9% 4 6% 5% 5% 6% 39%	2993
	11th to 20th	Night	2 8% 5% 11% 9% 5% 8% 6% 8% 11% 28%	2650
	21st to end	Night	2 11% 6% 15% 12% 5% 6% 6% 5% 5% 27%	2158
March	1st to 10th	Night	2 10% 8% 16% 10% 5% 6% 6% 7% 5% 26%	3815
	11th to 20th	Night	1 8% 5% 11% 12% 9% 10% 9% 6% 7% 22%	3703
	21st to end	Night	2 10% 5% 9% 7% 4 6% 7% 8% 9% 33%	3466
April	1st to 10th	Night	3 14% 7% 10% 8% 4 7% 6% 8% 8% 24%	1772
	11th to 20th	Night	3 11% 5% 10% 6% 3 5% 6% 7% 9% 35%	1503
	21st to end	Night	5% 8% 5% 6% 5% 4 6% 5% 6% 10% 39%	1312
May	1st to 10th	Night	6% 11% 3 8% 7% 4 7% 6% 8% 10% 29%	1080
	11th to 20th	Night	9% 10% 3 7% 5% 4 6% 5% 8% 7% 36%	860
	21st to end	Night	13% 8% 4 6% 7% 4 4 6% 7% 9% 33%	776
June	1st to 10th	Night	14% 12% 5% 8% 9% 5% 8% 6% 7% 7% 20%	582
	11th to 20th	Night	20% 11% 4 7% 7% 4 4 5% 5% 7% 26%	360
	21st to end	Night	21% 8% 2 9% 7% 5% 8% 6% 7% 8% 22%	360
July	1st to 10th	Night	16% 10% 4 8% 8% 5% 6% 5% 5% 7% 26%	545
	11th to 20th	Night	26% 11% 6% 9% 9% 3 7% 4 5% 6% 14%	720
	21st to end	Night	23% 8% 4 9% 8% 3 5% 5% 6% 8% 21%	900
August	1st to 10th	Night	26% 11% 4 8% 8% 4 7% 5% 6% 6% 15%	1074
	11th to 20th	Night	22% 12% 4 9% 7% 4 6% 6% 5% 5% 20%	1208
	21st to end	Night	24% 15% 5% 7% 6% 3 6% 5% 5% 6% 18%	1584
September	1st to 10th	Night	19% 11% 3 8% 8% 5% 5% 5% 6% 7% 23%	1651
	11th to 20th	Night	21% 13% 5% 8% 7% 4 6% 4 5% 7% 20%	1801
	21st to end	Night	17% 19% 5% 9% 8% 4 5% 4 5% 5% 19%	2040
October	1st to 10th	Night	11% 17% 6% 10% 7% 5% 6% 6% 5% 6% 21%	2214
	11th to 20th	Night	8% 15% 7% 12% 7% 4 5% 5% 6% 7% 25%	2394
	21st to end	Night	6% 15% 6% 11% 9% 4 5% 5% 5% 7% 26%	2888
November	1st to 10th	Night	4 14% 7% 12% 8% 4 6% 5% 5% 6% 29%	2872
	11th to 20th	Night	5% 12% 7% 13% 13% 6% 7% 5% 4 5% 24%	3191
	21st to end	Night	3 9% 6% 10% 10% 5% 7% 6% 6% 7% 30%	3357
December	1st to 10th	Night	3 9% 4 11% 10% 6% 8% 6% 7% 8% 27%	3485
	11th to 20th	Night	2 10% 8% 13% 10% 5% 7% 6% 6% 7% 26%	4470
	21st to end	Night	2 6% 5% 12% 10% 5% 6% 7% 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	44% 10% 15% 20% 10%	2746
May	1st to 10th	Day	50% 12% 19% 16% 4	2880
	11th to 20th	Day	47% 12% 14% 20% 7%	3038
	21st to end	Day	50% 13% 16% 16% 5%	3500
June	1st to 10th	Day	61% 16% 14% 8% 1	3377
	11th to 20th	Day	62% 13% 12% 11% 3	3600
	21st to end	Day	62% 14% 16% 8%	3600
July	1st to 10th	Day	57% 14% 16% 12% 1	3322
	11th to 20th	Day	71% 11% 13% 5%	3141
	21st to end	Day	62% 15% 17% 5%	3227
August	1st to 10th	Day	69% 11% 13% 6% 1	2846
	11th to 20th	Day	66% 14% 13% 7%	2690
	21st to end	Day	72% 13% 9% 6% 1	2772
September	1st to 10th	Day	63% 13% 13% 10% 1	2306
	11th to 20th	Day	62% 13% 14% 10%	2159
	21st to end	Day	64% 10% 11% 12% 3	1918
October	1st to 10th	Day	62% 12% 12% 9% 4 1	1746
	11th to 20th	Day	54% 12% 18% 10% 4 1	1566
	21st to end	Day	53% 12% 15% 15% 4 1	1468
November	1st to 10th	Day	57% 10% 11% 13% 5% 3	1205
	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	36% 11% 14% 27% 11%	1312
May	1st to 10th	Night	47% 11% 19% 19% 3	1080
	11th to 20th	Night	42% 13% 17% 20% 8%	860
	21st to end	Night	45% 13% 17% 18% 7%	776
June	1st to 10th	Night	59% 14% 13% 12% 2	582
	11th to 20th	Night	56% 11% 15% 15% 2	360
	21st to end	Night	59% 16% 19% 6%	360
July	1st to 10th	Night	56% 11% 20% 11% 1	526
	11th to 20th	Night	69% 12% 14% 5%	696
	21st to end	Night	59% 16% 20% 6%	850
August	1st to 10th	Night	67% 16% 12% 5% 1	1068
	11th to 20th	Night	64% 13% 13% 10%	1208
	21st to end	Night	65% 14% 13% 7%	1584
September	1st to 10th	Night	59% 14% 15% 11% 1	1651
	11th to 20th	Night	64% 9% 14% 12% 1	1801
	21st to end	Night	66% 10% 10% 11% 3	2040
October	1st to 10th	Night	63% 12% 13% 8% 4 1	2214
	11th to 20th	Night	58% 10% 15% 12% 5% 1	2394
	21st to end	Night	56% 10% 14% 15% 5% 1	2888
November	1st to 10th	Night	54% 9% 12% 18% 5% 2	2872
	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% 23% 31% 24% 4	622
May	1st to 10th	Day	12% 12% 25% 31% 17% 4	603
	11th to 20th	Day	12% 13% 25% 27% 18% 5%	682
	21st to end	Day	19% 13% 23% 24% 16% 5%	874
June	1st to 10th	Day	19% 10% 21% 25% 19% 6%	926
	11th to 20th	Day	19% 8% 21% 26% 20% 6%	990
	21st to end	Day	21% 9% 19% 24% 19% 8%	990
July	1st to 10th	Day	21% 12% 22% 25% 16% 4	869
	11th to 20th	Day	31% 10% 18% 22% 14% 4	792
	21st to end	Day	24% 11% 19% 25% 15% 5%	845
August	1st to 10th	Day	29% 15% 24% 17% 11% 4	626
	11th to 20th	Day	31% 15% 21% 21% 10% 2	615
	21st to end	Day	33% 15% 20% 22% 9% 1	693
September	1st to 10th	Day	28% 15% 23% 19% 11% 4	588
	11th to 20th	Day	32% 19% 21% 17% 9% 2	539
	21st to end	Day	26% 12% 19% 20% 17% 5%	360
October	1st to 10th	Day	26% 18% 23% 17% 12% 4	360
	11th to 20th	Day	11% 8% 21% 28% 20% 11%	360
	21st to end	Day	13% 10% 20% 27% 22% 8%	396
November	1st to 10th	Day	11% 10% 19% 28% 21% 10%	319
	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% 15% 31% 32% 7%	506
May	1st to 10th	Night	10% 9% 16% 26% 32% 7%	360
	11th to 20th	Night	10% 12% 19% 30% 26% 3	209
	21st to end	Night	13% 10% 21% 26% 26% 4	195
June	1st to 10th	Night	17% 10% 17% 27% 26% 2	180
	11th to 20th	Night	24% 7% 13% 24% 26% 5%	180
	21st to end	Night	21% 8% 13% 22% 31% 5%	180
July	1st to 10th	Night	22% 9% 19% 21% 25% 5%	175
	11th to 20th	Night	31% 9% 18% 20% 18% 3	174
	21st to end	Night	26% 7% 21% 21% 20% 4	273
August	1st to 10th	Night	31% 13% 15% 20% 17% 4	358
	11th to 20th	Night	28% 10% 22% 21% 15% 3	420
	21st to end	Night	31% 11% 14% 19% 20% 6%	594
September	1st to 10th	Night	26% 14% 21% 17% 17% 5%	540
	11th to 20th	Night	30% 15% 17% 17% 14% 6%	540
	21st to end	Night	26% 10% 12% 26% 19% 6%	571
October	1st to 10th	Night	25% 15% 18% 20% 17% 5%	684
	11th to 20th	Night	14% 10% 18% 26% 24% 8%	810
	21st to end	Night	12% 10% 17% 32% 22% 7%	891
November	1st to 10th	Night	10% 9% 19% 31% 24% 6%	830
	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 2024-04-22 05:25:46. Version ac07

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