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 2025-02-06.

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	5% 9% 3 9% 7% 6% 6% 5% 7% 8% 34%	111496
	Night	4 9% 3 10% 7% 6% 7% 6% 8% 9% 32%	115277
Transparency	Day	45% 13% 15% 16% 8% 2	111248
	Night	47% 14% 16% 15% 7% 1	115171
Seeing	Day	14% 23% 32% 21% 9% 2	15400
	Night	9% 15% 38% 26% 11% 1	24084

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 15% 6% 14% 10% 8% 7% 6% 8% 8% 18%	3179
	11th to 20th	Day	3 10% 3 10% 6% 7% 7% 5% 9% 9% 31%	3202
	21st to end	Day	6% 12% 4 10% 7% 6% 6% 5% 8% 10% 26%	4004
February	1st to 10th	Day	2 12% 4 11% 11% 9% 8% 6% 8% 9% 20%	1676
	11th to 20th	Day	2 10% 4 11% 7% 7% 7% 6% 9% 9% 28%	1665
	21st to end	Day	1 14% 4 15% 12% 8% 8% 5% 6% 7% 19%	1469
March	1st to 10th	Day	1 11% 6% 14% 10% 8% 7% 6% 8% 8% 22%	3138
	11th to 20th	Day	2 11% 3 9% 7% 6% 7% 6% 7% 8% 35%	3477
	21st to end	Day	3 15% 5% 14% 10% 8% 7% 5% 7% 7% 18%	4009
April	1st to 10th	Day	4 14% 6% 13% 10% 9% 7% 6% 6% 7% 18%	2280
	11th to 20th	Day	4 13% 5% 13% 9% 7% 7% 6% 7% 8% 21%	2298
	21st to end	Day	5% 13% 5% 13% 9% 8% 7% 4 6% 7% 23%	2608
May	1st to 10th	Day	7% 11% 3 9% 6% 6% 6% 5% 6% 6% 35%	4420
	11th to 20th	Day	6% 10% 3 9% 7% 6% 6% 5% 7% 10% 31%	4377
	21st to end	Day	15% 12% 5% 12% 8% 7% 6% 4 6% 6% 20%	4871
June	1st to 10th	Day	12% 9% 3 11% 7% 6% 7% 5% 7% 7% 27%	2850
	11th to 20th	Day	11% 10% 3 10% 10% 6% 6% 4 7% 8% 24%	2859
	21st to end	Day	6% 7% 3 7% 7% 6% 7% 5% 8% 8% 36%	2850
July	1st to 10th	Day	3 3 1 5% 4 4 4 3 6% 7% 59%	4740
	11th to 20th	Day	2 2 1 4 4 3 4 3 5% 6% 66%	4740
	21st to end	Day	3 4 2 4 4 4 5% 4 7% 8% 55%	4832
August	1st to 10th	Day	3 2 1 5% 4 5% 4 4 6% 8% 57%	4401
	11th to 20th	Day	3 4 2 6% 6% 5% 6% 5% 8% 9% 46%	4159
	21st to end	Day	6% 5% 2 7% 6% 6% 6% 5% 6% 9% 41%	4366
September	1st to 10th	Day	5% 5% 3 8% 5% 4 5% 3 5% 7% 49%	2280
	11th to 20th	Day	9% 8% 3 7% 6% 6% 6% 4 5% 7% 39%	2280
	21st to end	Day	9% 8% 3 8% 6% 5% 6% 5% 7% 9% 34%	2020
October	1st to 10th	Day	5% 6% 2 9% 7% 7% 6% 6% 8% 8% 37%	3180
	11th to 20th	Day	7% 9% 3 8% 7% 7% 7% 5% 8% 8% 30%	3161
	21st to end	Day	5% 8% 4 9% 7% 8% 7% 7% 10% 10% 25%	3115
November	1st to 10th	Day	6% 12% 5% 11% 8% 6% 7% 6% 8% 8% 22%	1568
	11th to 20th	Day	3 10% 4 11% 8% 9% 8% 7% 8% 10% 23%	1600
	21st to end	Day	3 12% 4 11% 7% 8% 7% 7% 8% 9% 25%	1600
December	1st to 10th	Day	2 8% 3 9% 8% 9% 7% 6% 8% 11% 28%	2393
	11th to 20th	Day	3 11% 4 13% 9% 9% 8% 8% 9% 8% 17%	2331
	21st to end	Day	3 7% 4 14% 10% 8% 9% 8% 10% 9% 18%	3498
January	1st to 10th	Night	2 13% 6% 14% 8% 9% 7% 6% 9% 10% 16%	6766
	11th to 20th	Night	3 9% 4 12% 7% 5% 6% 5% 8% 10% 31%	6693
	21st to end	Night	6% 11% 4 11% 7% 8% 7% 5% 7% 8% 27%	6952
February	1st to 10th	Night	3 14% 4 14% 9% 7% 6% 6% 10% 8% 18%	2610
	11th to 20th	Night	3 10% 3 9% 7% 6% 7% 6% 9% 10% 29%	2402
	21st to end	Night	3 11% 5% 13% 9% 7% 7% 6% 8% 9% 22%	1985
March	1st to 10th	Night	1 10% 5% 11% 8% 8% 8% 6% 8% 9% 25%	3736
	11th to 20th	Night	1 7% 2 8% 6% 6% 7% 5% 8% 10% 41%	3499
	21st to end	Night	4 12% 4 10% 8% 7% 7% 5% 8% 8% 27%	3643
April	1st to 10th	Night	2 12% 3 10% 8% 6% 7% 5% 8% 8% 30%	1900
	11th to 20th	Night	3 9% 3 8% 8% 7% 7% 7% 9% 10% 30%	1829
	21st to end	Night	5% 9% 4 9% 6% 6% 6% 4 8% 10% 33%	1572
May	1st to 10th	Night	4 8% 3 7% 6% 5% 5% 5% 6% 8% 43%	2540
	11th to 20th	Night	4 7% 3 7% 5% 5% 6% 5% 7% 8% 43%	2516
	21st to end	Night	9% 8% 3 9% 6% 6% 7% 6% 7% 9% 30%	2700
June	1st to 10th	Night	8% 8% 3 9% 7% 5% 5% 5% 7% 8% 35%	1330
	11th to 20th	Night	7% 7% 4 6% 6% 5% 5% 5% 8% 11% 36%	1238
	21st to end	Night	5% 5% 2 7% 6% 4 5% 4 7% 8% 46%	1330
July	1st to 10th	Night	2 3 2 4 3 3 3 3 4 8% 64%	2220
	11th to 20th	Night	2 2 2 2 3 3 3 5% 5% 72%	2220
	21st to end	Night	2 3 1 3 4 3 4 3 5% 9% 63%	2720
August	1st to 10th	Night	2 2 2 4 3 3 4 4 6% 9% 60%	2529
	11th to 20th	Night	2 3 1 5% 3 5% 5% 5% 8% 11% 51%	2673
	21st to end	Night	6% 3 2 6% 5% 5% 6% 6% 8% 9% 43%	3306
September	1st to 10th	Night	5% 4 1 5% 4 3 4 4 5% 8% 56%	1900
	11th to 20th	Night	6% 6% 3 7% 5% 4 5% 5% 6% 9% 46%	1900
	21st to end	Night	8% 7% 2 7% 5% 5% 5% 4 8% 9% 40%	2157
October	1st to 10th	Night	4 6% 2 7% 5% 6% 6% 5% 8% 10% 41%	3800
	11th to 20th	Night	3 6% 3 9% 6% 7% 9% 6% 9% 9% 34%	3777
	21st to end	Night	5% 9% 4 9% 6% 7% 7% 7% 9% 9% 29%	4443
November	1st to 10th	Night	6% 12% 4 12% 8% 7% 6% 7% 8% 9% 20%	2730
	11th to 20th	Night	3 11% 5% 11% 8% 8% 8% 6% 9% 8% 23%	2800
	21st to end	Night	4 14% 4 12% 8% 7% 8% 6% 7% 9% 20%	2800
December	1st to 10th	Night	3 8% 3 8% 6% 6% 7% 5% 10% 15% 30%	4719
	11th to 20th	Night	3 11% 5% 15% 9% 9% 9% 8% 9% 8% 13%	5884
	21st to end	Night	4 11% 5% 13% 9% 10% 9% 8% 10% 7% 14%	7458

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	59% 13% 13% 12% 3	3179
	11th to 20th	Day	46% 13% 17% 17% 3 4	3223
	21st to end	Day	53% 13% 13% 14% 7%	4004
February	1st to 10th	Day	58% 17% 12% 7% 6%	1676
	11th to 20th	Day	52% 15% 14% 11% 7% 1	1674
	21st to end	Day	63% 14% 9% 10% 3	1469
March	1st to 10th	Day	58% 14% 13% 10% 5%	3138
	11th to 20th	Day	44% 14% 17% 19% 6%	3477
	21st to end	Day	62% 14% 13% 6% 6%	4009
April	1st to 10th	Day	63% 15% 13% 7% 2	2280
	11th to 20th	Day	56% 16% 12% 8% 7%	2298
	21st to end	Day	58% 14% 14% 10% 5%	2608
May	1st to 10th	Day	43% 14% 14% 22% 6%	4420
	11th to 20th	Day	42% 17% 21% 17% 3	4380
	21st to end	Day	62% 13% 13% 9% 2	4872
June	1st to 10th	Day	53% 13% 13% 12% 6% 3	2850
	11th to 20th	Day	53% 15% 17% 12% 3	2859
	21st to end	Day	41% 15% 17% 19% 7% 1	2850
July	1st to 10th	Day	22% 7% 12% 23% 24% 12%	4666
	11th to 20th	Day	17% 8% 13% 25% 29% 9%	4659
	21st to end	Day	22% 10% 21% 26% 16% 6%	4679
August	1st to 10th	Day	21% 10% 13% 29% 25% 3	4384
	11th to 20th	Day	27% 13% 24% 26% 9% 1	4201
	21st to end	Day	35% 12% 22% 23% 7% 1	4365
September	1st to 10th	Day	35% 12% 13% 24% 12% 4	2280
	11th to 20th	Day	44% 12% 11% 18% 13% 3	2280
	21st to end	Day	47% 13% 16% 14% 8% 2	2020
October	1st to 10th	Day	40% 12% 19% 23% 7%	3180
	11th to 20th	Day	47% 14% 15% 20% 4	3161
	21st to end	Day	45% 20% 18% 13% 4	3115
November	1st to 10th	Day	59% 16% 12% 10% 3 1	1568
	11th to 20th	Day	56% 16% 13% 9% 5% 1	1600
	21st to end	Day	56% 16% 11% 10% 5% 1	1600
December	1st to 10th	Day	47% 16% 20% 12% 4	2393
	11th to 20th	Day	60% 15% 13% 7% 3	2333
	21st to end	Day	57% 21% 11% 9% 2	3498
January	1st to 10th	Night	59% 14% 13% 11% 3	6766
	11th to 20th	Night	47% 8% 18% 17% 6% 4	6734
	21st to end	Night	56% 11% 15% 14% 5%	6952
February	1st to 10th	Night	64% 11% 10% 9% 5% 1	2610
	11th to 20th	Night	54% 14% 14% 10% 7% 1	2404
	21st to end	Night	61% 13% 10% 10% 5% 1	1985
March	1st to 10th	Night	52% 18% 15% 10% 5%	3736
	11th to 20th	Night	40% 15% 15% 21% 9%	3500
	21st to end	Night	52% 18% 15% 8% 7%	3643
April	1st to 10th	Night	51% 18% 16% 11% 3	1900
	11th to 20th	Night	45% 21% 14% 12% 7% 1	1829
	21st to end	Night	48% 15% 18% 14% 5%	1572
May	1st to 10th	Night	39% 14% 17% 25% 4 1	2540
	11th to 20th	Night	40% 18% 22% 18% 3	2516
	21st to end	Night	51% 20% 16% 11% 2	2700
June	1st to 10th	Night	48% 15% 15% 13% 7% 2	1330
	11th to 20th	Night	41% 20% 19% 14% 6%	1238
	21st to end	Night	35% 17% 20% 19% 9% 2	1330
July	1st to 10th	Night	20% 8% 13% 28% 21% 10%	2185
	11th to 20th	Night	13% 9% 14% 34% 26% 4	2178
	21st to end	Night	18% 9% 21% 26% 17% 9%	2634
August	1st to 10th	Night	18% 11% 17% 26% 27% 2	2521
	11th to 20th	Night	21% 14% 33% 20% 10% 1	2697
	21st to end	Night	31% 15% 24% 21% 7% 1	3306
September	1st to 10th	Night	27% 14% 19% 25% 12% 2	1900
	11th to 20th	Night	36% 14% 15% 17% 14% 4	1900
	21st to end	Night	45% 15% 15% 15% 9% 2	2157
October	1st to 10th	Night	37% 14% 21% 22% 5% 1	3800
	11th to 20th	Night	43% 15% 15% 21% 5%	3777
	21st to end	Night	46% 13% 19% 17% 4	4443
November	1st to 10th	Night	62% 15% 11% 8% 3 1	2730
	11th to 20th	Night	60% 13% 12% 9% 5% 1	2800
	21st to end	Night	61% 15% 9% 9% 6% 1	2800
December	1st to 10th	Night	46% 14% 21% 16% 3	4719
	11th to 20th	Night	62% 17% 13% 7% 2	5881
	21st to end	Night	58% 19% 13% 8% 3	7458

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	9% 20% 42% 18% 10% 3	200
	11th to 20th	Day	9% 18% 41% 20% 12% 1	200
	21st to end	Day	9% 22% 40% 20% 9%	220
February	1st to 10th	Day	11% 24% 48% 13% 3 1	306
	11th to 20th	Day	7% 24% 39% 25% 3 1	365
	21st to end	Day	14% 25% 35% 19% 7% 1	334
March	1st to 10th	Day	13% 30% 29% 20% 8%	460
	11th to 20th	Day	15% 29% 25% 18% 12% 1	460
	21st to end	Day	18% 31% 27% 15% 8% 1	506
April	1st to 10th	Day	22% 27% 28% 17% 6%	460
	11th to 20th	Day	16% 30% 24% 20% 8% 3	452
	21st to end	Day	17% 30% 28% 16% 8% 2	460
May	1st to 10th	Day	14% 22% 32% 21% 9% 1	463
	11th to 20th	Day	14% 17% 34% 24% 9% 2	488
	21st to end	Day	17% 21% 33% 20% 7% 2	561
June	1st to 10th	Day	19% 30% 32% 14% 5% 1	680
	11th to 20th	Day	17% 26% 33% 18% 6% 1	689
	21st to end	Day	11% 22% 36% 21% 9% 1	680
July	1st to 10th	Day	9% 21% 35% 25% 8% 1	671
	11th to 20th	Day	8% 21% 34% 26% 9% 2	668
	21st to end	Day	6% 15% 34% 29% 12% 3	560
August	1st to 10th	Day	8% 12% 29% 30% 17% 5%	487
	11th to 20th	Day	9% 15% 28% 29% 15% 4	477
	21st to end	Day	10% 21% 35% 22% 9% 3	539
September	1st to 10th	Day	13% 23% 29% 22% 10% 3	490
	11th to 20th	Day	15% 23% 27% 23% 10% 2	490
	21st to end	Day	21% 23% 28% 18% 8% 1	490
October	1st to 10th	Day	18% 24% 24% 19% 12% 3	490
	11th to 20th	Day	21% 26% 26% 15% 10% 2	490
	21st to end	Day	19% 21% 33% 19% 7% 1	344
November	1st to 10th	Day	19% 19% 33% 20% 9% 1	200
	11th to 20th	Day	14% 23% 34% 16% 12% 3	200
	21st to end	Day	10% 20% 36% 23% 8% 4	200
December	1st to 10th	Day	13% 13% 26% 30% 16% 4	200
	11th to 20th	Day	14% 13% 43% 21% 7% 4	200
	21st to end	Day	10% 16% 38% 28% 8% 1	220
January	1st to 10th	Night	12% 22% 39% 20% 6% 1	900
	11th to 20th	Night	10% 17% 41% 25% 7%	890
	21st to end	Night	6% 17% 46% 23% 7% 1	880
February	1st to 10th	Night	10% 20% 44% 19% 5% 1	780
	11th to 20th	Night	7% 13% 48% 26% 6%	744
	21st to end	Night	8% 16% 42% 23% 11%	628
March	1st to 10th	Night	8% 18% 39% 23% 12%	760
	11th to 20th	Night	6% 22% 39% 21% 11% 1	760
	21st to end	Night	7% 18% 39% 25% 10% 1	836
April	1st to 10th	Night	10% 16% 33% 31% 9% 1	760
	11th to 20th	Night	8% 15% 41% 26% 9% 1	701
	21st to end	Night	10% 14% 38% 28% 10% 1	432
May	1st to 10th	Night	7% 12% 34% 32% 14% 1	380
	11th to 20th	Night	7% 9% 31% 37% 16%	374
	21st to end	Night	14% 9% 35% 30% 13%	411
June	1st to 10th	Night	11% 12% 42% 27% 9%	380
	11th to 20th	Night	9% 11% 43% 27% 10%	380
	21st to end	Night	6% 7% 40% 32% 14% 1	380
July	1st to 10th	Night	5% 7% 32% 41% 14% 1	370
	11th to 20th	Night	4 8% 34% 36% 17%	368
	21st to end	Night	4 6% 27% 41% 22% 1	416
August	1st to 10th	Night	5% 5% 19% 43% 27% 1	378
	11th to 20th	Night	4 4 27% 36% 28% 2	474
	21st to end	Night	6% 9% 30% 37% 16% 1	722
September	1st to 10th	Night	6% 10% 33% 29% 19% 2	760
	11th to 20th	Night	11% 8% 26% 28% 23% 4	760
	21st to end	Night	14% 16% 30% 26% 13% 1	760
October	1st to 10th	Night	12% 16% 29% 28% 14% 1	760
	11th to 20th	Night	12% 18% 35% 25% 10% 1	760
	21st to end	Night	13% 17% 39% 21% 8% 1	836
November	1st to 10th	Night	14% 19% 39% 23% 4	780
	11th to 20th	Night	11% 19% 43% 19% 8% 1	800
	21st to end	Night	12% 17% 42% 20% 7% 2	800
December	1st to 10th	Night	9% 15% 40% 24% 10% 2	894
	11th to 20th	Night	9% 19% 44% 20% 7% 1	1080
	21st to end	Night	9% 16% 48% 24% 4	990

Page generated at 2025-02-03 00:05:53. Version ac07

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