Keivers Lake
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Keivers Lake clear sky chart from 2005-11-06 to 2024-12-24.

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	9% 9% 3 8% 5% 5% 5% 4 6% 8% 37%	106001
	Night	7% 9% 4 9% 6% 5% 5% 4 7% 8% 35%	102682
Transparency	Day	44% 3 15% 26% 10% 1	105743
	Night	46% 3 14% 24% 10% 2	102586
Seeing	Day	12% 6% 24% 31% 20% 7%	15524
	Night	12% 5% 28% 36% 16% 2	24671

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	3 12% 6% 11% 7% 5% 5% 5% 7% 7% 32%	2219
	11th to 20th	Day	4 9% 4 11% 6% 5% 7% 5% 8% 7% 33%	2199
	21st to end	Day	5% 8% 3 9% 7% 6% 4 4 6% 8% 39%	2762
February	1st to 10th	Day	6% 14% 5% 11% 7% 6% 6% 4 7% 8% 27%	1520
	11th to 20th	Day	7% 13% 4 10% 8% 6% 6% 6% 7% 8% 26%	1655
	21st to end	Day	4 14% 6% 12% 8% 6% 5% 5% 6% 6% 26%	1498
March	1st to 10th	Day	3 13% 6% 13% 8% 7% 7% 4 6% 6% 27%	3138
	11th to 20th	Day	6% 9% 3 7% 5% 5% 4 3 7% 10% 41%	3475
	21st to end	Day	9% 20% 7% 14% 5% 4 4 3 5% 5% 24%	3855
April	1st to 10th	Day	8% 12% 4 9% 5% 6% 5% 6% 6% 8% 30%	2354
	11th to 20th	Day	11% 13% 4 9% 5% 5% 5% 4 7% 8% 29%	2440
	21st to end	Day	12% 10% 3 8% 6% 5% 4 4 6% 9% 32%	2470
May	1st to 10th	Day	21% 12% 3 7% 4 5% 4 4 5% 6% 28%	4411
	11th to 20th	Day	11% 9% 3 7% 5% 6% 5% 5% 7% 9% 32%	4694
	21st to end	Day	16% 9% 3 8% 6% 7% 6% 5% 7% 8% 26%	5161
June	1st to 10th	Day	16% 6% 2 6% 5% 5% 5% 5% 7% 10% 31%	2850
	11th to 20th	Day	18% 8% 3 8% 6% 6% 6% 5% 8% 6% 27%	2850
	21st to end	Day	9% 5% 2 5% 6% 5% 6% 5% 8% 10% 39%	2850
July	1st to 10th	Day	8% 4 1 5% 4 4 5% 4 6% 10% 50%	4740
	11th to 20th	Day	7% 4 1 4 3 4 5% 5% 6% 11% 49%	4740
	21st to end	Day	5% 4 2 4 3 4 5% 4 6% 9% 54%	5112
August	1st to 10th	Day	8% 6% 3 6% 4 5% 6% 5% 7% 9% 42%	4401
	11th to 20th	Day	7% 5% 2 6% 4 4 6% 5% 8% 12% 41%	4068
	21st to end	Day	11% 4 2 4 3 4 4 4 6% 9% 49%	4521
September	1st to 10th	Day	11% 5% 2 6% 4 4 4 4 6% 7% 47%	2376
	11th to 20th	Day	16% 8% 2 6% 3 3 4 3 4 7% 44%	2090
	21st to end	Day	9% 8% 2 6% 4 5% 4 3 6% 9% 44%	2090
October	1st to 10th	Day	7% 7% 2 6% 5% 5% 5% 4 7% 8% 42%	3312
	11th to 20th	Day	6% 7% 3 8% 5% 5% 4 4 6% 10% 40%	2922
	21st to end	Day	8% 8% 3 8% 6% 5% 5% 3 6% 6% 42%	3101
November	1st to 10th	Day	10% 16% 6% 11% 4 5% 5% 4 6% 7% 27%	1597
	11th to 20th	Day	7% 13% 4 10% 6% 4 5% 4 6% 7% 33%	1515
	21st to end	Day	5% 12% 3 12% 6% 6% 5% 5% 6% 7% 32%	1400
December	1st to 10th	Day	7% 13% 5% 10% 8% 7% 5% 4 5% 6% 29%	1400
	11th to 20th	Day	5% 11% 5% 12% 8% 6% 5% 4 6% 8% 30%	1752
	21st to end	Day	4 9% 3 8% 6% 5% 5% 4 6% 8% 43%	2463
January	1st to 10th	Night	4 14% 5% 12% 7% 6% 6% 5% 8% 8% 25%	4726
	11th to 20th	Night	3 9% 4 14% 7% 6% 6% 5% 6% 8% 31%	4699
	21st to end	Night	4 11% 5% 11% 5% 6% 4 5% 7% 8% 33%	4926
February	1st to 10th	Night	6% 12% 5% 13% 7% 6% 5% 4 6% 8% 27%	2660
	11th to 20th	Night	5% 13% 5% 11% 7% 7% 6% 4 7% 6% 28%	2412
	21st to end	Night	3 12% 4 9% 8% 5% 5% 5% 8% 9% 31%	1955
March	1st to 10th	Night	3 10% 4 15% 10% 8% 7% 5% 7% 6% 25%	3736
	11th to 20th	Night	7% 8% 3 7% 6% 5% 6% 5% 7% 9% 37%	3504
	21st to end	Night	7% 20% 7% 16% 6% 5% 5% 5% 6% 6% 16%	3785
April	1st to 10th	Night	9% 11% 4 9% 7% 4 5% 4 6% 9% 30%	1825
	11th to 20th	Night	9% 12% 4 11% 7% 6% 5% 5% 6% 7% 29%	1691
	21st to end	Night	11% 9% 4 9% 5% 5% 6% 4 6% 8% 31%	1710
May	1st to 10th	Night	21% 12% 3 8% 5% 4 4 4 5% 6% 29%	2550
	11th to 20th	Night	9% 7% 3 7% 6% 6% 7% 5% 8% 9% 33%	2199
	21st to end	Night	18% 9% 3 9% 6% 6% 6% 5% 7% 7% 22%	2414
June	1st to 10th	Night	16% 8% 2 8% 6% 5% 5% 5% 7% 8% 30%	1330
	11th to 20th	Night	17% 8% 4 8% 8% 6% 7% 4 6% 7% 26%	1330
	21st to end	Night	11% 5% 2 6% 5% 6% 5% 6% 6% 9% 39%	1330
July	1st to 10th	Night	7% 5% 2 6% 5% 6% 6% 5% 6% 8% 44%	2220
	11th to 20th	Night	5% 3 2 5% 4 4 5% 5% 9% 12% 46%	2220
	21st to end	Night	4 5% 2 5% 4 4 4 3 6% 10% 52%	2438
August	1st to 10th	Night	10% 6% 3 6% 4 5% 4 3 6% 9% 44%	2529
	11th to 20th	Night	6% 5% 3 7% 6% 5% 5% 4 8% 11% 40%	2768
	21st to end	Night	8% 5% 2 6% 4 4 5% 4 7% 10% 47%	3146
September	1st to 10th	Night	10% 5% 2 5% 3 4 5% 3 6% 8% 48%	1800
	11th to 20th	Night	14% 7% 2 6% 3 4 4 4 5% 8% 44%	2090
	21st to end	Night	9% 6% 2 6% 4 4 4 3 8% 8% 46%	2090
October	1st to 10th	Night	8% 7% 2 5% 4 4 5% 4 6% 9% 46%	3662
	11th to 20th	Night	6% 8% 3 7% 5% 5% 5% 4 6% 9% 43%	3993
	21st to end	Night	6% 9% 4 8% 5% 5% 6% 4 6% 7% 41%	4457
November	1st to 10th	Night	9% 15% 4 8% 5% 5% 5% 4 5% 8% 31%	2679
	11th to 20th	Night	5% 10% 4 10% 7% 6% 5% 5% 7% 9% 32%	2882
	21st to end	Night	4 12% 4 11% 7% 7% 5% 4 7% 9% 32%	3000
December	1st to 10th	Night	6% 13% 4 11% 7% 6% 6% 4 5% 7% 31%	3000
	11th to 20th	Night	4 10% 5% 13% 8% 7% 7% 4 7% 7% 29%	3660
	21st to end	Night	4 8% 3 9% 5% 5% 5% 4 6% 8% 44%	5266

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	50% 3 12% 23% 11% 1	2219
	11th to 20th	Day	49% 4 11% 15% 17% 4	2220
	21st to end	Day	44% 3 13% 32% 8% 1	2762
February	1st to 10th	Day	54% 4 13% 18% 10% 1	1520
	11th to 20th	Day	54% 6% 14% 17% 8% 1	1664
	21st to end	Day	57% 3 10% 19% 11%	1498
March	1st to 10th	Day	57% 3 12% 16% 12%	3138
	11th to 20th	Day	39% 5% 17% 25% 14% 1	3476
	21st to end	Day	64% 3 10% 17% 6%	3855
April	1st to 10th	Day	50% 6% 15% 20% 9% 1	2354
	11th to 20th	Day	52% 4 10% 23% 10% 1	2440
	21st to end	Day	51% 3 13% 24% 8% 1	2470
May	1st to 10th	Day	57% 2 12% 23% 6%	4411
	11th to 20th	Day	47% 3 12% 28% 10%	4698
	21st to end	Day	55% 3 14% 20% 7% 1	5162
June	1st to 10th	Day	46% 5% 17% 22% 8% 1	2850
	11th to 20th	Day	54% 4 14% 21% 5% 1	2850
	21st to end	Day	37% 6% 20% 29% 8% 1	2850
July	1st to 10th	Day	31% 3 19% 30% 15% 2	4666
	11th to 20th	Day	29% 3 20% 37% 10% 1	4659
	21st to end	Day	27% 3 16% 31% 19% 5%	4950
August	1st to 10th	Day	38% 4 18% 33% 7% 1	4384
	11th to 20th	Day	36% 3 25% 29% 6% 1	4107
	21st to end	Day	33% 3 22% 32% 10% 1	4520
September	1st to 10th	Day	36% 4 17% 27% 12% 4	2376
	11th to 20th	Day	41% 3 14% 30% 10% 2	2090
	21st to end	Day	38% 4 16% 26% 12% 3	2090
October	1st to 10th	Day	40% 2 21% 30% 7% 1	3312
	11th to 20th	Day	39% 3 19% 25% 12% 2	2922
	21st to end	Day	43% 3 8% 36% 10% 1	3101
November	1st to 10th	Day	56% 4 11% 20% 8% 2	1597
	11th to 20th	Day	50% 4 13% 23% 9% 1	1515
	21st to end	Day	49% 4 17% 21% 8% 2	1400
December	1st to 10th	Day	57% 3 12% 16% 10% 2	1400
	11th to 20th	Day	53% 3 16% 23% 5% 1	1754
	21st to end	Day	40% 2 10% 25% 18% 5%	2463
January	1st to 10th	Night	55% 3 12% 21% 7% 2	4726
	11th to 20th	Night	51% 4 11% 16% 15% 3	4740
	21st to end	Night	47% 3 13% 26% 10% 1	4926
February	1st to 10th	Night	54% 4 10% 21% 11% 1	2660
	11th to 20th	Night	54% 4 10% 19% 11% 2	2413
	21st to end	Night	46% 4 13% 23% 12% 1	1955
March	1st to 10th	Night	57% 4 9% 22% 7% 1	3736
	11th to 20th	Night	42% 5% 18% 23% 10% 1	3504
	21st to end	Night	66% 3 11% 14% 5% 1	3785
April	1st to 10th	Night	50% 6% 12% 19% 12% 1	1825
	11th to 20th	Night	51% 4 11% 24% 8% 1	1691
	21st to end	Night	50% 3 13% 24% 8% 2	1710
May	1st to 10th	Night	57% 3 9% 24% 7%	2550
	11th to 20th	Night	45% 2 11% 30% 12%	2199
	21st to end	Night	61% 3 13% 18% 4 1	2414
June	1st to 10th	Night	51% 6% 13% 20% 9% 1	1330
	11th to 20th	Night	57% 4 13% 18% 6% 2	1330
	21st to end	Night	39% 6% 19% 27% 8% 1	1330
July	1st to 10th	Night	38% 4 16% 25% 15% 1	2185
	11th to 20th	Night	29% 5% 17% 38% 7% 4	2178
	21st to end	Night	29% 4 14% 32% 19% 2	2361
August	1st to 10th	Night	37% 3 17% 33% 9%	2521
	11th to 20th	Night	37% 3 24% 31% 6% 1	2795
	21st to end	Night	34% 3 22% 32% 8% 2	3146
September	1st to 10th	Night	34% 3 16% 27% 14% 6%	1800
	11th to 20th	Night	39% 4 15% 27% 11% 4	2090
	21st to end	Night	35% 4 15% 28% 15% 3	2090
October	1st to 10th	Night	36% 2 18% 29% 14% 1	3662
	11th to 20th	Night	39% 3 17% 28% 11% 2	3993
	21st to end	Night	43% 3 13% 30% 10% 1	4457
November	1st to 10th	Night	50% 4 10% 24% 10% 1	2679
	11th to 20th	Night	49% 3 15% 21% 11% 1	2882
	21st to end	Night	49% 4 16% 20% 8% 2	3000
December	1st to 10th	Night	52% 3 12% 21% 9% 2	3000
	11th to 20th	Night	52% 4 17% 21% 5% 1	3657
	21st to end	Night	39% 2 10% 28% 15% 5%	5266

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% 4 23% 39% 19% 8%	180
	11th to 20th	Day	7% 4 34% 31% 20% 3	180
	21st to end	Day	8% 8% 28% 24% 25% 7%	198
February	1st to 10th	Day	15% 9% 22% 35% 12% 7%	180
	11th to 20th	Day	10% 6% 26% 35% 18% 4	265
	21st to end	Day	7% 7% 23% 35% 22% 5%	310
March	1st to 10th	Day	9% 6% 28% 32% 18% 6%	460
	11th to 20th	Day	8% 4 25% 35% 21% 7%	460
	21st to end	Day	12% 6% 25% 31% 18% 8%	506
April	1st to 10th	Day	12% 9% 29% 31% 14% 5%	460
	11th to 20th	Day	15% 10% 27% 27% 16% 6%	452
	21st to end	Day	15% 8% 26% 30% 18% 3	460
May	1st to 10th	Day	19% 9% 21% 26% 19% 6%	546
	11th to 20th	Day	13% 6% 21% 34% 21% 6%	675
	21st to end	Day	17% 5% 20% 28% 22% 8%	734
June	1st to 10th	Day	16% 7% 23% 34% 16% 4	680
	11th to 20th	Day	19% 8% 23% 32% 15% 4	680
	21st to end	Day	8% 4 24% 32% 22% 10%	680
July	1st to 10th	Day	11% 4 18% 33% 25% 9%	671
	11th to 20th	Day	12% 3 19% 33% 25% 8%	668
	21st to end	Day	7% 3 21% 30% 29% 11%	725
August	1st to 10th	Day	11% 3 22% 30% 23% 10%	487
	11th to 20th	Day	8% 5% 18% 33% 29% 8%	477
	21st to end	Day	10% 6% 21% 31% 23% 9%	539
September	1st to 10th	Day	13% 6% 28% 28% 18% 7%	490
	11th to 20th	Day	18% 7% 23% 27% 20% 6%	490
	21st to end	Day	14% 12% 29% 27% 14% 5%	490
October	1st to 10th	Day	16% 7% 24% 28% 17% 7%	390
	11th to 20th	Day	10% 8% 34% 27% 16% 4	300
	21st to end	Day	16% 11% 28% 31% 12% 2	330
November	1st to 10th	Day	16% 5% 27% 35% 12% 4	300
	11th to 20th	Day	15% 8% 31% 31% 14% 2	257
	21st to end	Day	7% 6% 33% 30% 16% 9%	200
December	1st to 10th	Day	11% 4 32% 33% 16% 6%	200
	11th to 20th	Day	9% 7% 32% 34% 15% 4	200
	21st to end	Day	9% 2 23% 35% 24% 7%	204
January	1st to 10th	Night	11% 5% 32% 36% 14% 2	950
	11th to 20th	Night	11% 6% 33% 35% 13% 2	950
	21st to end	Night	11% 8% 28% 37% 14% 3	874
February	1st to 10th	Night	11% 8% 27% 35% 18% 3	760
	11th to 20th	Night	10% 5% 33% 37% 13% 1	744
	21st to end	Night	8% 3 25% 37% 22% 5%	628
March	1st to 10th	Night	10% 4 28% 39% 16% 3	760
	11th to 20th	Night	9% 4 30% 38% 15% 3	760
	21st to end	Night	13% 6% 26% 36% 17% 3	836
April	1st to 10th	Night	14% 6% 28% 34% 16% 3	685
	11th to 20th	Night	15% 6% 31% 36% 11% 1	563
	21st to end	Night	15% 8% 28% 35% 13% 1	570
May	1st to 10th	Night	17% 9% 26% 33% 15% 1	475
	11th to 20th	Night	10% 6% 30% 36% 17% 1	374
	21st to end	Night	21% 4 22% 31% 19% 2	411
June	1st to 10th	Night	17% 8% 26% 35% 11% 3	380
	11th to 20th	Night	18% 4 31% 29% 18% 1	380
	21st to end	Night	12% 3 22% 39% 22% 2	380
July	1st to 10th	Night	12% 2 15% 44% 25% 2	370
	11th to 20th	Night	10% 2 20% 46% 21% 2	368
	21st to end	Night	6% 3 19% 42% 28% 3	416
August	1st to 10th	Night	12% 3 16% 39% 27% 3	378
	11th to 20th	Night	10% 4 19% 40% 26% 2	533
	21st to end	Night	10% 4 22% 41% 24%	627
September	1st to 10th	Night	12% 3 24% 41% 18% 2	636
	11th to 20th	Night	17% 3 21% 37% 20% 2	760
	21st to end	Night	11% 4 29% 36% 18% 2	760
October	1st to 10th	Night	16% 4 25% 36% 17% 2	760
	11th to 20th	Night	11% 5% 30% 37% 15% 2	760
	21st to end	Night	11% 8% 31% 34% 14% 1	836
November	1st to 10th	Night	15% 7% 32% 34% 10% 2	924
	11th to 20th	Night	9% 7% 39% 31% 12% 3	1000
	21st to end	Night	9% 5% 35% 37% 12% 2	1000
December	1st to 10th	Night	12% 7% 31% 33% 15% 3	1000
	11th to 20th	Night	9% 6% 33% 36% 13% 2	1000
	21st to end	Night	12% 3 30% 37% 15% 3	1063

Page generated at 2024-12-21 02:13:50. Version ac07

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