Driggs
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Driggs clear sky chart from 2005-11-06 to 2024-10-25.

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	7% 13% 4 9% 4 4 4 3 5% 6% 41%	101566
	Night	7% 14% 5% 9% 4 4 4 3 5% 5% 40%	97437
Transparency	Day	43% 5% 9% 20% 16% 7%	101310
	Night	45% 5% 10% 20% 15% 6%	97282
Seeing	Day	17% 15% 29% 26% 11% 2	15450
	Night	17% 8% 22% 35% 16% 2	25051

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	7% 21% 9% 19% 5% 4 3 2 4 4 23%	2324
	11th to 20th	Day	7% 21% 6% 15% 6% 4 3 3 4 4 26%	2797
	21st to end	Day	5% 27% 10% 13% 4 3 2 2 3 4 27%	3146
February	1st to 10th	Day	10% 25% 8% 14% 5% 4 3 2 4 3 21%	1710
	11th to 20th	Day	9% 23% 8% 15% 6% 3 4 3 4 3 22%	1665
	21st to end	Day	7% 23% 9% 21% 7% 4 3 2 3 3 19%	1527
March	1st to 10th	Day	5% 21% 8% 17% 4 3 3 3 4 4 28%	3370
	11th to 20th	Day	5% 18% 6% 9% 4 3 3 2 3 4 43%	3490
	21st to end	Day	7% 30% 12% 17% 6% 4 3 2 3 3 12%	3825
April	1st to 10th	Day	12% 22% 7% 10% 4 4 3 3 4 5% 24%	2175
	11th to 20th	Day	9% 20% 6% 11% 6% 4 4 3 4 5% 27%	2408
	21st to end	Day	12% 20% 5% 8% 5% 4 4 3 6% 6% 27%	2470
May	1st to 10th	Day	8% 19% 5% 9% 5% 5% 5% 4 5% 6% 29%	4110
	11th to 20th	Day	6% 7% 2 6% 4 5% 5% 4 6% 8% 46%	4165
	21st to end	Day	10% 15% 4 9% 5% 5% 5% 4 5% 6% 33%	4825
June	1st to 10th	Day	12% 7% 3 6% 5% 5% 5% 5% 8% 8% 36%	2704
	11th to 20th	Day	13% 8% 3 6% 5% 4 4 4 5% 6% 41%	2850
	21st to end	Day	4 3 1 4 3 3 4 4 6% 6% 62%	2850
July	1st to 10th	Day	3 2 1 3 2 2 4 3 5% 8% 66%	4740
	11th to 20th	Day	2 3 1 3 3 4 5% 4 6% 9% 59%	4400
	21st to end	Day	3 4 1 5% 4 5% 5% 5% 8% 9% 52%	4454
August	1st to 10th	Day	5% 4 2 6% 5% 4 5% 4 6% 8% 51%	4092
	11th to 20th	Day	3 3 1 4 3 4 4 4 6% 8% 59%	4028
	21st to end	Day	4 3 1 4 3 3 4 3 5% 5% 63%	4498
September	1st to 10th	Day	6% 5% 1 4 4 3 4 3 4 6% 58%	2244
	11th to 20th	Day	9% 8% 2 5% 4 3 3 3 4 6% 52%	2090
	21st to end	Day	11% 7% 1 4 3 3 3 2 4 6% 55%	2090
October	1st to 10th	Day	13% 10% 3 7% 4 4 4 4 4 4 43%	1948
	11th to 20th	Day	11% 13% 4 6% 3 3 3 2 3 4 48%	1900
	21st to end	Day	12% 15% 4 6% 3 3 3 3 4 7% 40%	1981
November	1st to 10th	Day	17% 15% 7% 9% 3 3 3 3 3 4 34%	1670
	11th to 20th	Day	13% 21% 5% 7% 3 3 3 3 4 5% 32%	1520
	21st to end	Day	8% 17% 6% 13% 3 3 3 2 3 4 37%	1520
December	1st to 10th	Day	12% 19% 7% 12% 6% 4 2 2 3 5% 28%	1520
	11th to 20th	Day	11% 23% 7% 13% 5% 3 4 3 4 5% 22%	1926
	21st to end	Day	6% 17% 5% 14% 5% 4 4 3 5% 5% 32%	2534
January	1st to 10th	Night	5% 15% 8% 20% 6% 4 4 3 4 6% 25%	4650
	11th to 20th	Night	7% 25% 7% 16% 7% 4 3 2 3 4 22%	4166
	21st to end	Night	4 31% 9% 12% 4 3 3 2 3 4 25%	4521
February	1st to 10th	Night	8% 23% 8% 16% 6% 4 3 3 4 3 22%	2470
	11th to 20th	Night	8% 23% 10% 13% 6% 4 3 2 3 4 25%	2402
	21st to end	Night	7% 22% 8% 17% 6% 4 5% 4 4 4 20%	1922
March	1st to 10th	Night	5% 21% 6% 18% 5% 3 4 3 3 5% 27%	3503
	11th to 20th	Night	4 14% 5% 7% 4 3 4 3 5% 5% 47%	3490
	21st to end	Night	7% 22% 10% 11% 5% 5% 4 3 5% 6% 22%	3828
April	1st to 10th	Night	11% 20% 6% 9% 4 4 4 4 5% 5% 28%	2005
	11th to 20th	Night	10% 15% 4 9% 6% 5% 4 4 5% 5% 33%	1717
	21st to end	Night	9% 15% 4 6% 4 4 3 4 5% 6% 40%	1710
May	1st to 10th	Night	8% 19% 5% 7% 5% 4 4 3 5% 6% 35%	2860
	11th to 20th	Night	5% 6% 2 6% 5% 4 4 4 7% 8% 48%	2739
	21st to end	Night	9% 12% 3 7% 5% 4 5% 3 6% 7% 38%	2762
June	1st to 10th	Night	11% 7% 2 7% 4 5% 4 5% 7% 7% 40%	1471
	11th to 20th	Night	12% 8% 2 5% 4 3 3 3 6% 8% 47%	1330
	21st to end	Night	4 3 2 3 2 3 3 2 6% 6% 66%	1330
July	1st to 10th	Night	3 2 1 3 3 3 4 4 5% 5% 68%	2220
	11th to 20th	Night	2 1 1 2 3 3 3 4 7% 9% 64%	2558
	21st to end	Night	2 2 2 4 3 4 5% 5% 7% 7% 61%	3109
August	1st to 10th	Night	4 4 1 5% 4 3 5% 4 6% 7% 57%	2847
	11th to 20th	Night	2 3 2 5% 3 4 4 3 6% 9% 60%	2811
	21st to end	Night	4 4 1 3 2 3 2 2 4 5% 69%	3167
September	1st to 10th	Night	6% 4 1 4 4 3 3 3 5% 5% 64%	1933
	11th to 20th	Night	7% 6% 2 4 3 4 3 4 6% 5% 56%	2090
	21st to end	Night	9% 7% 2 4 2 2 2 2 3 6% 61%	2090
October	1st to 10th	Night	12% 9% 2 5% 4 3 3 2 4 6% 50%	2232
	11th to 20th	Night	13% 10% 3 5% 2 3 3 3 4 4 51%	2280
	21st to end	Night	12% 13% 3 6% 3 3 3 3 5% 6% 44%	2479
November	1st to 10th	Night	16% 16% 4 7% 4 3 3 3 4 5% 36%	2405
	11th to 20th	Night	11% 19% 5% 8% 4 3 4 3 4 5% 34%	2645
	21st to end	Night	9% 17% 5% 9% 4 4 3 3 5% 5% 37%	2660
December	1st to 10th	Night	9% 21% 6% 12% 6% 4 3 3 3 5% 27%	2660
	11th to 20th	Night	10% 21% 7% 13% 6% 4 4 3 4 4 24%	3271
	21st to end	Night	7% 19% 6% 12% 5% 4 4 3 4 5% 31%	5104

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	66% 3 10% 17% 3 1	2324
	11th to 20th	Day	60% 5% 12% 13% 9% 1	2797
	21st to end	Day	62% 6% 10% 15% 7% 1	3146
February	1st to 10th	Day	69% 4 10% 13% 4 1	1710
	11th to 20th	Day	64% 4 11% 12% 6% 2	1674
	21st to end	Day	69% 5% 5% 13% 6% 2	1527
March	1st to 10th	Day	57% 5% 8% 18% 11% 1	3370
	11th to 20th	Day	44% 5% 15% 24% 11% 1	3490
	21st to end	Day	76% 4 8% 10% 2	3825
April	1st to 10th	Day	61% 5% 10% 15% 7% 1	2175
	11th to 20th	Day	58% 4 10% 19% 9% 1	2411
	21st to end	Day	55% 5% 10% 24% 5%	2470
May	1st to 10th	Day	50% 6% 8% 25% 9% 1	4110
	11th to 20th	Day	33% 7% 10% 33% 13% 5%	4168
	21st to end	Day	49% 6% 10% 29% 7%	4825
June	1st to 10th	Day	42% 6% 15% 25% 11% 1	2704
	11th to 20th	Day	41% 4 9% 21% 17% 7%	2850
	21st to end	Day	21% 4 6% 27% 32% 11%	2850
July	1st to 10th	Day	14% 4 4 16% 36% 26%	4666
	11th to 20th	Day	19% 4 6% 14% 24% 33%	4321
	21st to end	Day	23% 6% 6% 18% 30% 16%	4314
August	1st to 10th	Day	27% 6% 6% 17% 28% 16%	4078
	11th to 20th	Day	21% 5% 6% 21% 34% 13%	4067
	21st to end	Day	21% 4 6% 20% 32% 18%	4497
September	1st to 10th	Day	26% 4 6% 17% 31% 15%	2244
	11th to 20th	Day	32% 4 7% 24% 24% 8%	2090
	21st to end	Day	31% 2 10% 28% 23% 6%	2090
October	1st to 10th	Day	44% 2 9% 25% 16% 3	1948
	11th to 20th	Day	41% 3 14% 29% 11% 2	1900
	21st to end	Day	45% 4 14% 24% 12% 1	1981
November	1st to 10th	Day	54% 4 12% 21% 8% 2	1670
	11th to 20th	Day	55% 4 15% 18% 8% 1	1520
	21st to end	Day	52% 4 14% 19% 9% 2	1520
December	1st to 10th	Day	61% 5% 11% 11% 8% 4	1520
	11th to 20th	Day	65% 5% 11% 14% 6%	1924
	21st to end	Day	53% 5% 9% 16% 9% 8%	2534
January	1st to 10th	Night	61% 5% 9% 18% 6% 1	4650
	11th to 20th	Night	67% 4 9% 11% 6% 2	4166
	21st to end	Night	65% 4 11% 12% 6% 1	4521
February	1st to 10th	Night	66% 5% 9% 14% 6%	2470
	11th to 20th	Night	64% 3 9% 15% 8% 1	2403
	21st to end	Night	65% 4 8% 14% 7% 2	1922
March	1st to 10th	Night	57% 6% 7% 18% 11% 1	3503
	11th to 20th	Night	37% 5% 15% 30% 12% 1	3490
	21st to end	Night	60% 6% 14% 18% 2 1	3828
April	1st to 10th	Night	54% 5% 14% 16% 10% 1	2005
	11th to 20th	Night	51% 4 13% 21% 10% 2	1717
	21st to end	Night	42% 5% 15% 29% 9%	1710
May	1st to 10th	Night	46% 6% 9% 25% 12% 1	2860
	11th to 20th	Night	27% 8% 13% 36% 13% 3	2740
	21st to end	Night	40% 7% 11% 30% 11% 1	2762
June	1st to 10th	Night	39% 7% 14% 27% 12% 1	1471
	11th to 20th	Night	35% 4 10% 25% 19% 8%	1330
	21st to end	Night	18% 4 7% 27% 30% 14%	1330
July	1st to 10th	Night	15% 4 6% 15% 37% 24%	2185
	11th to 20th	Night	12% 5% 4 15% 33% 32%	2515
	21st to end	Night	18% 6% 6% 17% 32% 21%	3011
August	1st to 10th	Night	24% 6% 5% 18% 30% 18%	2838
	11th to 20th	Night	21% 4 5% 27% 28% 15%	2838
	21st to end	Night	17% 3 5% 24% 31% 20%	3167
September	1st to 10th	Night	22% 3 5% 20% 32% 19%	1933
	11th to 20th	Night	28% 4 10% 23% 25% 10%	2090
	21st to end	Night	27% 2 9% 27% 29% 6%	2090
October	1st to 10th	Night	37% 3 11% 25% 19% 4	2232
	11th to 20th	Night	36% 3 11% 34% 13% 2	2280
	21st to end	Night	40% 5% 15% 26% 13% 1	2479
November	1st to 10th	Night	51% 3 12% 22% 10% 2	2405
	11th to 20th	Night	53% 4 13% 20% 9% 2	2645
	21st to end	Night	49% 4 13% 21% 11% 2	2660
December	1st to 10th	Night	61% 4 13% 13% 6% 3	2660
	11th to 20th	Night	63% 5% 12% 14% 7%	3272
	21st to end	Night	54% 5% 8% 17% 9% 6%	5104

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	23% 21% 22% 23% 12% 1	180
	11th to 20th	Day	15% 17% 31% 24% 10% 2	253
	21st to end	Day	16% 12% 34% 26% 10% 1	297
February	1st to 10th	Day	24% 26% 32% 14% 3	270
	11th to 20th	Day	23% 22% 32% 17% 6% 1	270
	21st to end	Day	21% 24% 33% 17% 5%	339
March	1st to 10th	Day	26% 23% 32% 17% 3	460
	11th to 20th	Day	18% 17% 32% 25% 8% 1	460
	21st to end	Day	28% 20% 28% 19% 4	506
April	1st to 10th	Day	32% 19% 24% 19% 5% 1	460
	11th to 20th	Day	23% 23% 29% 17% 6% 1	452
	21st to end	Day	26% 15% 25% 23% 10% 2	460
May	1st to 10th	Day	17% 18% 29% 25% 10% 1	463
	11th to 20th	Day	20% 10% 27% 25% 15% 2	543
	21st to end	Day	22% 10% 20% 25% 19% 4	734
June	1st to 10th	Day	13% 13% 24% 28% 18% 4	680
	11th to 20th	Day	22% 15% 29% 23% 10% 1	680
	21st to end	Day	8% 12% 30% 30% 15% 4	680
July	1st to 10th	Day	7% 11% 27% 33% 18% 4	671
	11th to 20th	Day	6% 8% 39% 35% 11% 1	556
	21st to end	Day	6% 8% 29% 40% 14% 3	531
August	1st to 10th	Day	9% 9% 34% 33% 12% 2	487
	11th to 20th	Day	6% 11% 29% 35% 16% 4	477
	21st to end	Day	11% 13% 26% 32% 14% 4	539
September	1st to 10th	Day	9% 11% 33% 29% 16% 3	490
	11th to 20th	Day	18% 18% 26% 23% 14% 2	490
	21st to end	Day	17% 12% 27% 29% 13% 2	490
October	1st to 10th	Day	16% 13% 26% 27% 17% 1	348
	11th to 20th	Day	18% 17% 22% 26% 12% 5%	300
	21st to end	Day	25% 14% 28% 25% 6% 1	311
November	1st to 10th	Day	26% 19% 28% 18% 7% 3	270
	11th to 20th	Day	22% 16% 30% 21% 9% 2	270
	21st to end	Day	16% 15% 33% 27% 9%	270
December	1st to 10th	Day	23% 14% 30% 21% 10% 2	270
	11th to 20th	Day	24% 19% 31% 21% 5% 1	270
	21st to end	Day	24% 17% 28% 21% 7% 2	223
January	1st to 10th	Night	18% 12% 23% 35% 12% 1	900
	11th to 20th	Night	20% 11% 22% 32% 13% 2	760
	21st to end	Night	14% 9% 28% 35% 12% 2	836
February	1st to 10th	Night	20% 13% 27% 30% 8% 2	760
	11th to 20th	Night	19% 12% 25% 32% 10% 2	744
	21st to end	Night	18% 13% 27% 30% 10% 2	628
March	1st to 10th	Night	20% 11% 25% 32% 10% 1	760
	11th to 20th	Night	18% 8% 24% 34% 14% 1	760
	21st to end	Night	19% 10% 25% 32% 12% 1	836
April	1st to 10th	Night	21% 13% 23% 29% 12% 2	675
	11th to 20th	Night	20% 8% 27% 34% 10% 1	563
	21st to end	Night	18% 5% 22% 33% 20% 2	570
May	1st to 10th	Night	17% 7% 20% 34% 21% 2	570
	11th to 20th	Night	15% 3 22% 35% 22% 3	561
	21st to end	Night	20% 7% 16% 34% 20% 3	617
June	1st to 10th	Night	16% 6% 20% 36% 20% 2	521
	11th to 20th	Night	17% 8% 20% 38% 17%	380
	21st to end	Night	5% 2 20% 42% 28% 3	380
July	1st to 10th	Night	4 2 16% 46% 28% 4	370
	11th to 20th	Night	4 3 18% 45% 28% 1	453
	21st to end	Night	4 3 16% 43% 31% 3	624
August	1st to 10th	Night	8% 4 15% 41% 30% 2	567
	11th to 20th	Night	4 3 16% 41% 32% 4	564
	21st to end	Night	7% 6% 17% 38% 30% 3	627
September	1st to 10th	Night	8% 3 19% 39% 28% 3	603
	11th to 20th	Night	9% 6% 16% 35% 27% 6%	760
	21st to end	Night	13% 3 21% 36% 21% 6%	760
October	1st to 10th	Night	17% 5% 19% 38% 19% 3	760
	11th to 20th	Night	19% 7% 15% 36% 20% 3	760
	21st to end	Night	19% 7% 20% 38% 13% 3	812
November	1st to 10th	Night	24% 10% 22% 30% 13% 2	740
	11th to 20th	Night	23% 11% 24% 34% 7% 1	935
	21st to end	Night	19% 11% 23% 34% 12% 2	950
December	1st to 10th	Night	22% 10% 27% 31% 9% 1	950
	11th to 20th	Night	24% 11% 22% 34% 8% 1	950
	21st to end	Night	23% 12% 24% 30% 9% 2	1045

Page generated at 2024-10-22 18:21:01. Version ac07

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