Lytton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Lytton clear sky chart from 2005-11-06 to 2026-06-01.

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	4 8% 3 9% 7% 7% 7% 5% 8% 8% 34%	135264
	Night	3 8% 3 9% 7% 7% 7% 6% 8% 9% 33%	136448
Transparency	Day	42% 14% 17% 18% 8% 2	134975
	Night	44% 15% 17% 16% 7% 1	136315
Seeing	Day	14% 22% 32% 21% 9% 2	17132
	Night	9% 15% 37% 27% 11% 1	25730

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 13% 5% 12% 9% 8% 8% 6% 9% 9% 18%	4125
	11th to 20th	Day	3 8% 3 8% 6% 7% 7% 4 8% 9% 38%	4176
	21st to end	Day	5% 10% 4 10% 7% 7% 7% 6% 9% 10% 25%	5186
February	1st to 10th	Day	2 11% 4 11% 10% 9% 8% 7% 8% 9% 20%	1806
	11th to 20th	Day	2 10% 4 11% 7% 7% 7% 7% 9% 9% 28%	1845
	21st to end	Day	1 13% 5% 16% 12% 8% 8% 5% 6% 8% 18%	1619
March	1st to 10th	Day	1 10% 5% 14% 9% 7% 7% 6% 9% 9% 24%	4618
	11th to 20th	Day	1 8% 3 10% 9% 9% 9% 7% 9% 8% 27%	5083
	21st to end	Day	3 11% 4 12% 10% 9% 9% 7% 8% 9% 17%	5875
April	1st to 10th	Day	4 13% 5% 13% 9% 9% 7% 6% 6% 8% 20%	2520
	11th to 20th	Day	4 12% 5% 13% 9% 7% 7% 6% 7% 8% 22%	2544
	21st to end	Day	5% 12% 5% 12% 8% 8% 7% 5% 6% 7% 26%	2882
May	1st to 10th	Day	5% 9% 3 8% 5% 5% 6% 5% 7% 7% 39%	6460
	11th to 20th	Day	5% 8% 3 11% 8% 8% 8% 6% 8% 9% 25%	6417
	21st to end	Day	10% 9% 4 9% 7% 6% 6% 4 7% 8% 31%	7145
June	1st to 10th	Day	11% 8% 3 11% 7% 5% 7% 5% 7% 8% 28%	3001
	11th to 20th	Day	10% 10% 3 10% 9% 6% 6% 4 7% 8% 25%	3009
	21st to end	Day	6% 7% 3 7% 7% 6% 7% 5% 8% 9% 36%	3000
July	1st to 10th	Day	2 3 2 5% 4 4 4 4 7% 9% 56%	6780
	11th to 20th	Day	3 3 1 4 4 4 4 3 5% 7% 62%	6780
	21st to end	Day	3 3 2 4 4 4 5% 4 6% 8% 56%	6930
August	1st to 10th	Day	3 2 1 5% 4 5% 4 5% 6% 8% 56%	4541
	11th to 20th	Day	3 4 2 6% 6% 5% 6% 5% 8% 9% 46%	4293
	21st to end	Day	5% 5% 2 7% 6% 6% 6% 5% 6% 9% 42%	4504
September	1st to 10th	Day	5% 5% 3 7% 5% 4 5% 3 6% 7% 49%	2400
	11th to 20th	Day	9% 8% 3 7% 5% 5% 6% 4 5% 7% 41%	2400
	21st to end	Day	8% 8% 3 8% 6% 6% 6% 5% 7% 9% 34%	2126
October	1st to 10th	Day	5% 6% 2 8% 6% 7% 6% 6% 8% 9% 37%	3280
	11th to 20th	Day	7% 9% 3 8% 7% 7% 7% 5% 8% 8% 30%	3261
	21st to end	Day	5% 8% 4 10% 7% 8% 7% 7% 10% 10% 25%	3215
November	1st to 10th	Day	6% 12% 5% 12% 8% 7% 6% 6% 8% 8% 22%	1648
	11th to 20th	Day	3 10% 4 12% 8% 9% 8% 6% 9% 10% 22%	1680
	21st to end	Day	3 12% 4 11% 7% 8% 7% 7% 9% 9% 24%	1680
December	1st to 10th	Day	2 8% 3 9% 8% 9% 7% 7% 8% 11% 28%	2467
	11th to 20th	Day	3 10% 4 13% 9% 9% 8% 8% 9% 9% 17%	2393
	21st to end	Day	3 7% 4 14% 10% 8% 9% 8% 10% 9% 18%	3575
January	1st to 10th	Night	2 12% 6% 13% 8% 9% 8% 6% 10% 10% 16%	8770
	11th to 20th	Night	2 7% 3 9% 6% 5% 6% 5% 8% 10% 37%	8719
	21st to end	Night	4 9% 3 10% 7% 8% 8% 6% 8% 8% 28%	8994
February	1st to 10th	Night	3 13% 4 13% 9% 7% 6% 7% 10% 9% 19%	2809
	11th to 20th	Night	3 10% 3 9% 8% 7% 7% 6% 9% 10% 29%	2662
	21st to end	Night	3 10% 5% 13% 9% 8% 7% 6% 8% 8% 22%	2187
March	1st to 10th	Night	1 8% 4 10% 8% 8% 7% 6% 9% 10% 29%	5496
	11th to 20th	Night	1 5% 2 8% 7% 7% 7% 7% 11% 12% 34%	5120
	21st to end	Night	4 10% 3 9% 8% 7% 8% 6% 9% 8% 26%	5341
April	1st to 10th	Night	3 11% 3 10% 8% 6% 7% 6% 9% 9% 29%	2100
	11th to 20th	Night	3 8% 3 8% 8% 7% 7% 7% 9% 11% 30%	2023
	21st to end	Night	4 8% 4 9% 6% 6% 6% 5% 8% 10% 35%	1737
May	1st to 10th	Night	3 6% 2 6% 5% 5% 6% 5% 7% 8% 47%	3720
	11th to 20th	Night	4 7% 3 9% 6% 6% 6% 6% 9% 9% 34%	3696
	21st to end	Night	6% 6% 2 7% 5% 6% 6% 6% 7% 9% 39%	3968
June	1st to 10th	Night	8% 8% 3 9% 7% 5% 5% 5% 7% 8% 36%	1400
	11th to 20th	Night	7% 6% 4 6% 6% 5% 5% 5% 8% 11% 36%	1303
	21st to end	Night	6% 6% 2 7% 6% 4 5% 4 8% 8% 46%	1400
July	1st to 10th	Night	2 3 2 5% 4 4 4 3 6% 8% 59%	3180
	11th to 20th	Night	2 2 1 2 2 3 3 3 5% 5% 73%	3180
	21st to end	Night	3 3 1 4 4 4 4 3 5% 7% 61%	3913
August	1st to 10th	Night	2 3 2 4 3 3 4 4 6% 10% 59%	2609
	11th to 20th	Night	2 3 1 5% 3 5% 5% 5% 8% 11% 51%	2758
	21st to end	Night	6% 3 2 6% 5% 5% 6% 6% 8% 9% 44%	3410
September	1st to 10th	Night	4 4 1 6% 4 3 4 4 5% 8% 56%	2000
	11th to 20th	Night	6% 6% 2 6% 5% 4 5% 5% 6% 9% 47%	2000
	21st to end	Night	8% 7% 2 7% 5% 5% 5% 4 8% 9% 40%	2271
October	1st to 10th	Night	4 6% 2 7% 5% 6% 6% 5% 8% 10% 41%	3920
	11th to 20th	Night	3 6% 3 9% 6% 6% 9% 6% 9% 9% 34%	3897
	21st to end	Night	5% 9% 4 8% 6% 7% 7% 7% 10% 9% 29%	4585
November	1st to 10th	Night	6% 12% 4 12% 8% 7% 6% 7% 9% 9% 19%	2870
	11th to 20th	Night	3 11% 5% 11% 8% 8% 8% 6% 9% 8% 23%	2940
	21st to end	Night	4 14% 4 12% 8% 7% 8% 7% 8% 9% 20%	2940
December	1st to 10th	Night	3 8% 3 9% 7% 6% 7% 5% 10% 14% 29%	4864
	11th to 20th	Night	3 11% 5% 15% 9% 9% 9% 8% 9% 8% 13%	6043
	21st to end	Night	4 10% 5% 13% 9% 10% 9% 8% 10% 8% 14%	7623

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	53% 15% 18% 12% 2	4125
	11th to 20th	Day	40% 12% 18% 22% 5% 3	4197
	21st to end	Day	52% 12% 13% 17% 6%	5187
February	1st to 10th	Day	56% 17% 12% 7% 7% 1	1806
	11th to 20th	Day	51% 15% 14% 13% 7% 1	1854
	21st to end	Day	62% 14% 10% 10% 3 1	1619
March	1st to 10th	Day	52% 14% 14% 12% 8%	4618
	11th to 20th	Day	41% 17% 17% 19% 6%	5083
	21st to end	Day	53% 17% 15% 10% 5%	5875
April	1st to 10th	Day	59% 15% 14% 9% 2	2520
	11th to 20th	Day	54% 16% 14% 9% 7% 1	2544
	21st to end	Day	55% 14% 13% 11% 6% 1	2882
May	1st to 10th	Day	36% 13% 13% 29% 9%	6460
	11th to 20th	Day	44% 17% 22% 15% 2	6420
	21st to end	Day	47% 13% 17% 20% 3 1	7146
June	1st to 10th	Day	51% 13% 14% 14% 6% 3	3001
	11th to 20th	Day	52% 15% 16% 13% 4	3009
	21st to end	Day	40% 14% 18% 19% 7% 1	3000
July	1st to 10th	Day	21% 9% 18% 23% 20% 9%	6706
	11th to 20th	Day	19% 8% 20% 25% 22% 6%	6699
	21st to end	Day	20% 9% 25% 25% 17% 5%	6735
August	1st to 10th	Day	21% 10% 13% 29% 25% 3	4524
	11th to 20th	Day	27% 13% 24% 26% 9% 1	4335
	21st to end	Day	34% 12% 22% 23% 8% 2	4503
September	1st to 10th	Day	34% 11% 14% 25% 13% 4	2400
	11th to 20th	Day	42% 11% 12% 19% 13% 2	2400
	21st to end	Day	46% 13% 17% 14% 7% 2	2126
October	1st to 10th	Day	39% 12% 20% 23% 6%	3280
	11th to 20th	Day	48% 13% 14% 20% 5%	3261
	21st to end	Day	44% 20% 19% 13% 4	3215
November	1st to 10th	Day	58% 16% 13% 10% 2 1	1648
	11th to 20th	Day	57% 16% 14% 8% 5% 1	1680
	21st to end	Day	55% 17% 11% 10% 5% 1	1680
December	1st to 10th	Day	47% 16% 20% 12% 4	2467
	11th to 20th	Day	60% 16% 14% 7% 3	2395
	21st to end	Day	57% 21% 12% 9% 2	3575
January	1st to 10th	Night	56% 15% 15% 11% 3	8770
	11th to 20th	Night	40% 10% 18% 22% 7% 3	8760
	21st to end	Night	51% 12% 14% 17% 6%	8994
February	1st to 10th	Night	61% 12% 11% 10% 6% 1	2809
	11th to 20th	Night	52% 14% 14% 10% 8% 1	2664
	21st to end	Night	60% 14% 11% 10% 5% 1	2187
March	1st to 10th	Night	44% 18% 16% 16% 6%	5496
	11th to 20th	Night	37% 16% 17% 20% 10%	5121
	21st to end	Night	48% 19% 15% 10% 7%	5341
April	1st to 10th	Night	49% 18% 18% 12% 3	2100
	11th to 20th	Night	43% 22% 14% 13% 7% 1	2023
	21st to end	Night	45% 15% 19% 14% 7%	1737
May	1st to 10th	Night	32% 14% 22% 25% 7%	3717
	11th to 20th	Night	41% 18% 23% 15% 2	3696
	21st to end	Night	41% 17% 19% 20% 3	3968
June	1st to 10th	Night	46% 15% 16% 14% 8% 2	1400
	11th to 20th	Night	41% 19% 19% 15% 6%	1303
	21st to end	Night	34% 17% 21% 18% 8% 1	1400
July	1st to 10th	Night	22% 10% 20% 26% 15% 7%	3145
	11th to 20th	Night	12% 9% 26% 32% 19% 3	3138
	21st to end	Night	20% 9% 23% 26% 16% 7%	3803
August	1st to 10th	Night	18% 11% 18% 26% 26% 2	2601
	11th to 20th	Night	22% 14% 33% 19% 11% 1	2782
	21st to end	Night	31% 15% 24% 22% 7% 2	3410
September	1st to 10th	Night	27% 14% 19% 26% 13% 2	2000
	11th to 20th	Night	35% 13% 16% 18% 14% 3	2000
	21st to end	Night	44% 15% 15% 15% 9% 2	2271
October	1st to 10th	Night	37% 14% 22% 21% 5% 1	3920
	11th to 20th	Night	43% 15% 15% 21% 5%	3897
	21st to end	Night	46% 14% 19% 17% 4	4585
November	1st to 10th	Night	61% 16% 12% 8% 3 1	2870
	11th to 20th	Night	59% 14% 12% 9% 5% 1	2940
	21st to end	Night	60% 15% 10% 9% 5% 1	2940
December	1st to 10th	Night	46% 15% 21% 16% 3	4864
	11th to 20th	Night	62% 16% 13% 7% 2	6040
	21st to end	Night	57% 19% 13% 8% 3	7623

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	10% 19% 42% 17% 10% 3	220
	11th to 20th	Day	8% 17% 39% 21% 13% 1	220
	21st to end	Day	10% 21% 39% 23% 8%	242
February	1st to 10th	Day	11% 22% 48% 14% 4 1	346
	11th to 20th	Day	6% 23% 39% 26% 4 1	425
	21st to end	Day	17% 24% 34% 18% 7% 1	388
March	1st to 10th	Day	16% 27% 28% 21% 7%	540
	11th to 20th	Day	19% 27% 25% 17% 11% 1	540
	21st to end	Day	20% 30% 27% 15% 7% 1	594
April	1st to 10th	Day	21% 25% 28% 17% 7% 1	540
	11th to 20th	Day	17% 27% 26% 19% 8% 3	532
	21st to end	Day	17% 27% 28% 17% 8% 2	540
May	1st to 10th	Day	15% 22% 34% 21% 8% 1	543
	11th to 20th	Day	14% 19% 35% 22% 9% 2	568
	21st to end	Day	19% 21% 33% 19% 6% 2	653
June	1st to 10th	Day	18% 30% 32% 15% 5% 1	731
	11th to 20th	Day	17% 25% 33% 19% 6% 1	739
	21st to end	Day	12% 20% 37% 22% 9% 1	730
July	1st to 10th	Day	10% 21% 35% 24% 8% 1	721
	11th to 20th	Day	8% 20% 34% 27% 8% 2	718
	21st to end	Day	6% 15% 34% 29% 12% 4	605
August	1st to 10th	Day	7% 12% 30% 30% 17% 5%	527
	11th to 20th	Day	10% 15% 28% 28% 14% 4	517
	21st to end	Day	9% 19% 33% 24% 11% 4	583
September	1st to 10th	Day	12% 21% 28% 22% 12% 4	530
	11th to 20th	Day	15% 22% 26% 25% 10% 3	530
	21st to end	Day	21% 24% 28% 18% 8% 1	530
October	1st to 10th	Day	18% 24% 25% 18% 12% 3	530
	11th to 20th	Day	23% 24% 26% 15% 10% 2	530
	21st to end	Day	20% 21% 32% 19% 6% 1	378
November	1st to 10th	Day	19% 19% 35% 18% 8%	220
	11th to 20th	Day	14% 21% 36% 16% 10% 3	220
	21st to end	Day	11% 20% 35% 23% 7% 4	220
December	1st to 10th	Day	14% 12% 27% 29% 15% 3	220
	11th to 20th	Day	16% 13% 40% 20% 6% 4	220
	21st to end	Day	11% 15% 38% 28% 7% 1	242
January	1st to 10th	Night	12% 21% 39% 21% 6% 1	950
	11th to 20th	Night	10% 16% 39% 26% 8%	939
	21st to end	Night	6% 16% 44% 25% 8% 1	924
February	1st to 10th	Night	9% 19% 44% 21% 6% 1	840
	11th to 20th	Night	6% 12% 45% 27% 8% 1	824
	21st to end	Night	9% 16% 43% 22% 10%	692
March	1st to 10th	Night	9% 18% 38% 23% 12%	840
	11th to 20th	Night	8% 21% 38% 21% 11% 1	840
	21st to end	Night	8% 19% 38% 24% 10% 1	924
April	1st to 10th	Night	10% 16% 32% 31% 10% 1	840
	11th to 20th	Night	9% 15% 39% 26% 10% 1	775
	21st to end	Night	10% 13% 37% 29% 10% 1	477
May	1st to 10th	Night	7% 11% 34% 34% 14% 1	420
	11th to 20th	Night	7% 9% 32% 37% 16%	414
	21st to end	Night	13% 9% 34% 31% 13%	455
June	1st to 10th	Night	10% 11% 43% 27% 9%	400
	11th to 20th	Night	9% 10% 44% 28% 10%	400
	21st to end	Night	7% 6% 40% 32% 15% 1	400
July	1st to 10th	Night	6% 7% 33% 39% 14% 1	390
	11th to 20th	Night	4 8% 35% 36% 17%	388
	21st to end	Night	4 6% 27% 39% 23% 1	438
August	1st to 10th	Night	5% 5% 20% 43% 27% 1	398
	11th to 20th	Night	4 4 27% 36% 27% 2	499
	21st to end	Night	6% 9% 29% 37% 19% 1	760
September	1st to 10th	Night	6% 10% 31% 30% 21% 2	800
	11th to 20th	Night	10% 8% 25% 30% 23% 4	800
	21st to end	Night	15% 16% 30% 26% 13% 1	800
October	1st to 10th	Night	12% 15% 29% 28% 14% 1	800
	11th to 20th	Night	12% 18% 35% 25% 10% 1	800
	21st to end	Night	14% 17% 38% 21% 8% 1	880
November	1st to 10th	Night	15% 20% 38% 23% 5%	820
	11th to 20th	Night	11% 19% 42% 20% 8% 1	840
	21st to end	Night	12% 17% 41% 21% 7% 2	840
December	1st to 10th	Night	10% 15% 40% 24% 10% 2	939
	11th to 20th	Night	12% 19% 43% 20% 6% 1	1139
	21st to end	Night	9% 16% 47% 25% 4	1045

Page generated at 2026-05-28 22:53:27. Version ac07

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