The Meadow
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the The Meadow clear sky chart from 2005-11-06 to 2025-04-11.

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% 9% 4 8% 5% 4 4 4 6% 7% 37%	113738
	Night	11% 10% 4 9% 5% 4 4 4 5% 6% 37%	114778
Transparency	Day	46% 4 13% 25% 12% 1	117334
	Night	47% 3 12% 23% 13% 1	119324
Seeing	Day	16% 11% 30% 26% 13% 3	16504
	Night	16% 9% 31% 32% 11% 1	26575

By Month

Percentage Cloud Cover SE (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	8% 13% 5% 20% 8% 6% 5% 3 4 6% 23%	3617
	11th to 20th	Day	5% 12% 7% 15% 7% 5% 8% 8% 9% 5% 20%	3620
	21st to end	Day	7% 15% 7% 13% 5% 4 4 3 4 6% 30%	4442
February	1st to 10th	Day	8% 11% 5% 10% 6% 6% 6% 5% 6% 7% 29%	1800
	11th to 20th	Day	8% 10% 5% 11% 6% 6% 4 4 6% 6% 34%	1754
	21st to end	Day	11% 11% 4 9% 6% 5% 4 4 5% 7% 33%	1580
March	1st to 10th	Day	12% 9% 3 5% 4 3 3 3 5% 7% 47%	4746
	11th to 20th	Day	10% 9% 3 7% 4 4 4 3 5% 9% 40%	4980
	21st to end	Day	22% 11% 3 10% 5% 4 5% 3 5% 6% 26%	5593
April	1st to 10th	Day	17% 11% 4 7% 4 4 3 3 6% 6% 33%	2400
	11th to 20th	Day	20% 12% 4 7% 5% 4 4 3 4 5% 31%	2254
	21st to end	Day	20% 12% 3 7% 4 5% 5% 4 6% 6% 28%	2434
May	1st to 10th	Day	17% 7% 2 7% 4 4 4 4 5% 7% 40%	4321
	11th to 20th	Day	13% 7% 2 6% 4 4 5% 4 6% 7% 43%	4399
	21st to end	Day	17% 8% 3 6% 5% 4 4 3 5% 6% 36%	4824
June	1st to 10th	Day	12% 5% 2 5% 4 5% 4 4 5% 8% 46%	2660
	11th to 20th	Day	13% 6% 3 7% 5% 5% 5% 5% 6% 9% 37%	2660
	21st to end	Day	11% 5% 2 7% 5% 6% 5% 5% 7% 8% 40%	2660
July	1st to 10th	Day	11% 6% 2 6% 5% 5% 6% 4 8% 10% 37%	4440
	11th to 20th	Day	5% 3 1 4 3 4 4 3 6% 8% 59%	4440
	21st to end	Day	7% 4 2 6% 5% 5% 5% 4 6% 9% 47%	4813
August	1st to 10th	Day	12% 6% 3 5% 4 4 5% 4 7% 8% 41%	4115
	11th to 20th	Day	13% 6% 2 6% 4 4 5% 4 7% 7% 43%	4041
	21st to end	Day	9% 5% 3 7% 5% 5% 4 3 6% 8% 45%	4277
September	1st to 10th	Day	12% 6% 2 5% 4 4 4 3 5% 7% 47%	2280
	11th to 20th	Day	13% 6% 2 5% 4 4 3 4 6% 8% 45%	2280
	21st to end	Day	15% 7% 2 6% 4 3 3 3 6% 7% 43%	1988
October	1st to 10th	Day	15% 7% 2 6% 4 3 4 3 5% 6% 45%	1900
	11th to 20th	Day	15% 11% 2 7% 4 4 5% 3 5% 7% 38%	1900
	21st to end	Day	16% 14% 4 7% 3 3 4 3 4 6% 36%	2033
November	1st to 10th	Day	13% 11% 5% 8% 5% 4 4 3 5% 6% 35%	1687
	11th to 20th	Day	12% 15% 7% 10% 6% 4 4 4 5% 5% 29%	1600
	21st to end	Day	12% 13% 4 10% 5% 4 3 3 5% 7% 34%	1600
December	1st to 10th	Day	7% 10% 4 13% 13% 7% 5% 4 6% 6% 23%	2610
	11th to 20th	Day	11% 14% 6% 12% 7% 5% 4 4 5% 5% 26%	3008
	21st to end	Day	17% 20% 8% 20% 6% 4 3 3 3 4 13%	3982
January	1st to 10th	Night	6% 12% 6% 16% 9% 6% 4 3 5% 5% 28%	6348
	11th to 20th	Night	7% 12% 5% 13% 8% 7% 8% 9% 8% 5% 19%	6360
	21st to end	Night	8% 17% 7% 11% 6% 4 4 3 5% 6% 30%	6520
February	1st to 10th	Night	6% 12% 5% 11% 7% 7% 4 4 5% 7% 32%	2600
	11th to 20th	Night	6% 10% 4 9% 6% 6% 5% 4 5% 7% 38%	2533
	21st to end	Night	11% 10% 4 9% 6% 5% 5% 4 4 5% 36%	2048
March	1st to 10th	Night	10% 7% 3 7% 5% 4 4 3 5% 6% 46%	5152
	11th to 20th	Night	9% 7% 3 8% 5% 5% 5% 4 6% 9% 39%	4980
	21st to end	Night	24% 13% 4 9% 4 3 3 3 4 5% 28%	5335
April	1st to 10th	Night	16% 13% 2 7% 4 3 4 3 5% 7% 36%	2000
	11th to 20th	Night	21% 10% 4 7% 4 5% 3 3 5% 5% 34%	1881
	21st to end	Night	17% 9% 3 6% 4 4 5% 2 5% 6% 37%	1743
May	1st to 10th	Night	14% 8% 3 7% 4 4 4 4 5% 6% 40%	2583
	11th to 20th	Night	14% 5% 2 4 3 3 3 3 5% 7% 51%	2506
	21st to end	Night	13% 7% 3 7% 5% 4 4 4 5% 6% 42%	2743
June	1st to 10th	Night	12% 5% 2 5% 4 3 5% 3 7% 7% 47%	1520
	11th to 20th	Night	10% 4 2 7% 4 5% 3 4 6% 7% 46%	1520
	21st to end	Night	7% 5% 2 5% 4 4 5% 4 6% 8% 50%	1520
July	1st to 10th	Night	10% 4 2 4 4 4 4 4 6% 10% 48%	2530
	11th to 20th	Night	4 2 1 4 3 3 4 4 6% 10% 58%	2530
	21st to end	Night	5% 3 2 5% 3 3 4 3 6% 8% 58%	2750
August	1st to 10th	Night	11% 6% 3 7% 5% 4 4 3 5% 7% 45%	2822
	11th to 20th	Night	13% 5% 2 5% 3 3 3 3 5% 8% 49%	2798
	21st to end	Night	9% 6% 3 7% 4 4 4 4 5% 6% 47%	3380
September	1st to 10th	Night	10% 4 2 5% 3 4 4 3 4 8% 53%	1900
	11th to 20th	Night	10% 4 3 5% 3 3 4 3 4 8% 53%	1900
	21st to end	Night	13% 5% 2 4 3 3 4 3 4 7% 50%	2170
October	1st to 10th	Night	14% 6% 2 6% 4 3 4 3 4 6% 50%	2280
	11th to 20th	Night	15% 10% 3 6% 4 3 4 3 4 7% 42%	2280
	21st to end	Night	17% 12% 4 7% 3 4 3 3 4 7% 37%	2564
November	1st to 10th	Night	12% 10% 3 6% 5% 4 3 3 5% 6% 41%	2607
	11th to 20th	Night	12% 12% 5% 11% 5% 5% 4 4 5% 5% 32%	2800
	21st to end	Night	13% 11% 4 9% 5% 4 4 3 4 7% 36%	2800
December	1st to 10th	Night	7% 8% 5% 15% 8% 8% 5% 4 5% 7% 29%	4580
	11th to 20th	Night	10% 15% 6% 16% 7% 4 5% 4 4 5% 23%	5199
	21st to end	Night	20% 16% 7% 17% 6% 4 4 3 3 4 16%	6996

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	64% 3 8% 19% 6%	3618
	11th to 20th	Day	61% 3 7% 17% 11% 1	3620
	21st to end	Day	55% 3 15% 18% 7%	4442
February	1st to 10th	Day	53% 4 14% 18% 10% 1	1800
	11th to 20th	Day	49% 5% 11% 26% 9% 1	1763
	21st to end	Day	50% 5% 13% 21% 11% 1	1580
March	1st to 10th	Day	38% 2 18% 26% 13% 3	4746
	11th to 20th	Day	42% 2 14% 30% 10% 1	4980
	21st to end	Day	60% 2 10% 18% 10% 1	5595
April	1st to 10th	Day	51% 4 10% 21% 12% 1	2400
	11th to 20th	Day	55% 4 8% 19% 12% 2	2254
	21st to end	Day	54% 5% 12% 20% 8%	2434
May	1st to 10th	Day	43% 5% 11% 25% 14% 2	4361
	11th to 20th	Day	40% 5% 11% 28% 14% 2	4403
	21st to end	Day	48% 4 10% 25% 11% 1	4837
June	1st to 10th	Day	35% 5% 14% 30% 13% 1	2660
	11th to 20th	Day	42% 6% 14% 23% 14% 1	2660
	21st to end	Day	40% 6% 15% 27% 11% 2	2660
July	1st to 10th	Day	42% 4 19% 24% 10% 1	4371
	11th to 20th	Day	24% 3 16% 36% 18% 2	4365
	21st to end	Day	34% 5% 14% 29% 18% 1	4662
August	1st to 10th	Day	40% 4 12% 29% 14% 1	4100
	11th to 20th	Day	39% 4 12% 35% 10%	4080
	21st to end	Day	39% 3 15% 29% 13% 1	4276
September	1st to 10th	Day	36% 5% 12% 32% 14%	2280
	11th to 20th	Day	38% 4 16% 33% 9%	2280
	21st to end	Day	40% 5% 11% 33% 11%	1988
October	1st to 10th	Day	30% 2 8% 37% 23%	3160
	11th to 20th	Day	41% 2 11% 26% 19% 1	3140
	21st to end	Day	44% 2 14% 29% 9%	3335
November	1st to 10th	Day	49% 4 13% 19% 13% 2	1687
	11th to 20th	Day	57% 4 12% 17% 9% 1	1600
	21st to end	Day	51% 4 17% 20% 7% 2	1600
December	1st to 10th	Day	61% 4 15% 14% 5%	2610
	11th to 20th	Day	60% 2 12% 19% 7%	3005
	21st to end	Day	78% 2 7% 9% 4	3982
January	1st to 10th	Night	59% 2 9% 20% 9%	6348
	11th to 20th	Night	62% 3 10% 13% 12%	6360
	21st to end	Night	56% 3 11% 22% 8%	6520
February	1st to 10th	Night	52% 4 11% 22% 10% 1	2600
	11th to 20th	Night	44% 5% 14% 27% 9% 1	2534
	21st to end	Night	49% 5% 11% 22% 12% 2	2048
March	1st to 10th	Night	39% 3 13% 24% 17% 4	5152
	11th to 20th	Night	42% 3 14% 25% 15% 1	4980
	21st to end	Night	60% 2 9% 17% 11%	5335
April	1st to 10th	Night	48% 4 9% 22% 16% 1	2000
	11th to 20th	Night	52% 4 8% 19% 14% 2	1881
	21st to end	Night	48% 4 9% 22% 15% 2	1743
May	1st to 10th	Night	44% 4 12% 19% 20% 1	2608
	11th to 20th	Night	33% 4 9% 30% 19% 4	2507
	21st to end	Night	42% 4 12% 25% 16% 1	2751
June	1st to 10th	Night	34% 5% 13% 30% 17% 2	1520
	11th to 20th	Night	36% 5% 14% 23% 19% 3	1520
	21st to end	Night	30% 6% 15% 31% 15% 3	1520
July	1st to 10th	Night	33% 3 23% 26% 13% 2	2490
	11th to 20th	Night	21% 4 15% 38% 21% 2	2482
	21st to end	Night	25% 4 15% 33% 20% 3	2662
August	1st to 10th	Night	39% 4 11% 29% 14% 4	2813
	11th to 20th	Night	36% 3 13% 33% 14% 2	2825
	21st to end	Night	38% 3 16% 28% 12% 2	3380
September	1st to 10th	Night	30% 5% 12% 36% 16% 1	1900
	11th to 20th	Night	31% 4 16% 32% 16%	1900
	21st to end	Night	34% 4 14% 33% 15% 1	2170
October	1st to 10th	Night	26% 2 6% 36% 26% 4	3800
	11th to 20th	Night	35% 2 11% 26% 23% 2	3779
	21st to end	Night	47% 2 11% 27% 13%	4212
November	1st to 10th	Night	45% 3 13% 24% 14% 1	2607
	11th to 20th	Night	53% 4 12% 18% 11% 1	2800
	21st to end	Night	50% 4 15% 23% 7% 1	2800
December	1st to 10th	Night	55% 4 17% 20% 4	4580
	11th to 20th	Night	65% 3 10% 16% 6% 1	5201
	21st to end	Night	73% 2 8% 12% 5%	6996

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	12% 16% 31% 28% 10% 2	300
	11th to 20th	Day	16% 15% 39% 24% 5% 1	300
	21st to end	Day	13% 12% 39% 25% 10% 2	330
February	1st to 10th	Day	15% 15% 48% 16% 6% 1	300
	11th to 20th	Day	12% 20% 42% 20% 5% 1	300
	21st to end	Day	16% 18% 39% 26% 1	249
March	1st to 10th	Day	16% 14% 47% 17% 6% 1	300
	11th to 20th	Day	19% 15% 37% 21% 7% 2	300
	21st to end	Day	25% 15% 29% 20% 8% 3	384
April	1st to 10th	Day	25% 17% 31% 21% 6%	500
	11th to 20th	Day	28% 16% 23% 25% 8% 1	452
	21st to end	Day	27% 13% 28% 21% 10% 2	614
May	1st to 10th	Day	20% 13% 33% 23% 10% 2	653
	11th to 20th	Day	19% 13% 27% 24% 13% 3	675
	21st to end	Day	19% 9% 28% 25% 16% 4	734
June	1st to 10th	Day	11% 9% 25% 33% 17% 4	680
	11th to 20th	Day	15% 9% 33% 30% 11% 2	680
	21st to end	Day	12% 7% 28% 30% 16% 6%	680
July	1st to 10th	Day	9% 4 21% 31% 24% 11%	671
	11th to 20th	Day	8% 6% 27% 30% 21% 8%	668
	21st to end	Day	7% 4 24% 37% 21% 8%	739
August	1st to 10th	Day	11% 5% 21% 33% 23% 7%	676
	11th to 20th	Day	15% 5% 20% 31% 25% 5%	665
	21st to end	Day	12% 4 25% 33% 22% 5%	597
September	1st to 10th	Day	14% 7% 27% 31% 16% 6%	490
	11th to 20th	Day	14% 4 27% 31% 21% 3	490
	21st to end	Day	19% 14% 26% 24% 14% 4	317
October	1st to 10th	Day	16% 14% 27% 26% 14% 3	300
	11th to 20th	Day	21% 16% 35% 20% 7%	300
	21st to end	Day	25% 15% 36% 17% 5% 2	330
November	1st to 10th	Day	19% 13% 36% 20% 11% 1	300
	11th to 20th	Day	20% 18% 39% 20% 4	300
	21st to end	Day	23% 14% 38% 20% 5%	300
December	1st to 10th	Day	15% 9% 44% 23% 7% 1	300
	11th to 20th	Day	20% 17% 39% 19% 6%	300
	21st to end	Day	25% 16% 36% 18% 4 1	330
January	1st to 10th	Night	12% 14% 36% 30% 9% 1	1000
	11th to 20th	Night	17% 12% 35% 30% 6% 1	1000
	21st to end	Night	18% 12% 35% 28% 7% 1	1100
February	1st to 10th	Night	12% 14% 40% 27% 7% 1	1000
	11th to 20th	Night	12% 14% 41% 26% 7% 1	979
	21st to end	Night	18% 12% 34% 29% 8%	728
March	1st to 10th	Night	16% 11% 37% 27% 8% 1	709
	11th to 20th	Night	16% 13% 36% 28% 6% 1	600
	21st to end	Night	23% 10% 31% 26% 8% 2	660
April	1st to 10th	Night	21% 14% 34% 25% 6%	600
	11th to 20th	Night	27% 10% 29% 27% 7% 1	565
	21st to end	Night	20% 10% 32% 28% 9% 1	570
May	1st to 10th	Night	20% 10% 31% 33% 5% 1	570
	11th to 20th	Night	19% 8% 29% 33% 10% 1	561
	21st to end	Night	12% 9% 26% 38% 15%	617
June	1st to 10th	Night	13% 4 28% 40% 14% 1	570
	11th to 20th	Night	12% 5% 33% 41% 9% 1	570
	21st to end	Night	10% 4 23% 46% 16% 1	570
July	1st to 10th	Night	7% 2 20% 42% 28% 2	555
	11th to 20th	Night	6% 3 22% 46% 21% 2	552
	21st to end	Night	5% 2 20% 48% 23% 2	624
August	1st to 10th	Night	7% 5% 15% 49% 24% 1	567
	11th to 20th	Night	14% 2 18% 37% 26% 3	564
	21st to end	Night	10% 3 24% 38% 23% 2	627
September	1st to 10th	Night	10% 5% 23% 41% 16% 4	570
	11th to 20th	Night	11% 7% 26% 37% 17% 2	570
	21st to end	Night	15% 10% 29% 30% 15% 1	670
October	1st to 10th	Night	16% 8% 29% 32% 13% 2	760
	11th to 20th	Night	18% 11% 34% 29% 7% 1	760
	21st to end	Night	24% 12% 27% 30% 7%	836
November	1st to 10th	Night	19% 9% 34% 29% 8% 1	851
	11th to 20th	Night	18% 13% 35% 27% 7% 1	1000
	21st to end	Night	19% 14% 34% 26% 7% 1	1000
December	1st to 10th	Night	16% 9% 37% 29% 7% 1	1000
	11th to 20th	Night	19% 10% 39% 25% 6% 1	1000
	21st to end	Night	25% 10% 34% 25% 5%	1100

Page generated at 2025-04-08 08:17:24. Version ac07

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