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 2024-10-24.

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	13% 9% 3 8% 5% 4 4 4 6% 7% 37%	101506
	Night	12% 9% 4 9% 5% 4 4 4 5% 6% 38%	97373
Transparency	Day	46% 4 13% 25% 11% 1	101298
	Night	46% 4 12% 24% 12% 1	97252
Seeing	Day	16% 11% 30% 26% 14% 3	15984
	Night	16% 9% 31% 32% 11% 1	25825

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	11% 17% 6% 18% 6% 4 4 3 4 6% 21%	2527
	11th to 20th	Day	5% 14% 5% 15% 10% 6% 8% 7% 6% 4 20%	2530
	21st to end	Day	10% 20% 7% 13% 5% 4 4 3 5% 6% 23%	3103
February	1st to 10th	Day	8% 11% 5% 10% 6% 6% 6% 5% 5% 7% 30%	1710
	11th to 20th	Day	8% 10% 5% 11% 6% 6% 5% 4 5% 6% 34%	1664
	21st to end	Day	11% 12% 4 9% 6% 5% 4 4 5% 7% 32%	1503
March	1st to 10th	Day	12% 10% 4 6% 5% 3 4 3 5% 7% 42%	3302
	11th to 20th	Day	10% 10% 3 8% 4 5% 4 3 5% 8% 39%	3480
	21st to end	Day	22% 13% 4 11% 6% 4 5% 3 4 5% 23%	3903
April	1st to 10th	Day	18% 11% 4 7% 4 4 3 3 6% 6% 33%	2280
	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%	1956
November	1st to 10th	Day	12% 11% 5% 8% 5% 4 4 3 5% 6% 36%	1601
	11th to 20th	Day	12% 14% 7% 10% 7% 4 4 4 5% 5% 28%	1520
	21st to end	Day	13% 12% 3 9% 5% 4 3 3 5% 7% 35%	1520
December	1st to 10th	Day	12% 13% 5% 12% 8% 6% 5% 4 4 6% 25%	1520
	11th to 20th	Day	10% 12% 6% 12% 7% 5% 5% 4 5% 5% 27%	1918
	21st to end	Day	19% 17% 7% 18% 6% 3 3 3 3 4 17%	2783
January	1st to 10th	Night	9% 16% 8% 16% 6% 5% 4 3 4 4 25%	4428
	11th to 20th	Night	7% 12% 4 14% 8% 7% 7% 7% 7% 5% 21%	4440
	21st to end	Night	11% 19% 8% 13% 5% 4 4 3 4 4 24%	4562
February	1st to 10th	Night	5% 12% 5% 11% 7% 7% 4 4 5% 6% 33%	2470
	11th to 20th	Night	6% 10% 4 8% 6% 6% 5% 4 6% 7% 38%	2403
	21st to end	Night	12% 10% 4 9% 6% 5% 5% 4 3 5% 36%	1949
March	1st to 10th	Night	9% 8% 3 7% 5% 4 4 3 5% 7% 46%	3582
	11th to 20th	Night	8% 8% 3 9% 6% 5% 5% 4 6% 7% 40%	3480
	21st to end	Night	25% 13% 4 11% 4 3 3 2 3 5% 28%	3727
April	1st to 10th	Night	16% 12% 2 7% 4 3 4 3 5% 7% 35%	1900
	11th to 20th	Night	21% 10% 4 7% 4 5% 3 3 5% 5% 34%	1875
	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	16% 12% 4 7% 3 4 3 3 4 7% 37%	2466
November	1st to 10th	Night	12% 10% 3 6% 5% 4 3 3 5% 6% 42%	2473
	11th to 20th	Night	12% 12% 5% 11% 5% 5% 4 4 5% 5% 32%	2660
	21st to end	Night	13% 10% 4 9% 5% 4 4 3 4 7% 37%	2660
December	1st to 10th	Night	10% 12% 5% 12% 7% 5% 4 3 5% 6% 30%	2660
	11th to 20th	Night	11% 13% 6% 12% 7% 5% 5% 4 4 7% 26%	3279
	21st to end	Night	21% 15% 5% 13% 6% 4 3 3 4 4 20%	4884

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% 4 10% 16% 3	2528
	11th to 20th	Day	65% 4 9% 16% 6%	2530
	21st to end	Day	62% 4 14% 16% 4	3103
February	1st to 10th	Day	52% 4 14% 19% 10% 1	1710
	11th to 20th	Day	49% 5% 11% 25% 9% 1	1673
	21st to end	Day	51% 5% 12% 20% 12% 1	1503
March	1st to 10th	Day	42% 3 16% 25% 13% 1	3302
	11th to 20th	Day	44% 3 10% 32% 9% 1	3480
	21st to end	Day	64% 3 10% 18% 6%	3903
April	1st to 10th	Day	51% 4 11% 22% 12% 1	2280
	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	40% 3 12% 31% 13% 1	1900
	11th to 20th	Day	47% 3 14% 24% 12% 1	1900
	21st to end	Day	51% 4 12% 23% 10% 1	1956
November	1st to 10th	Day	49% 4 12% 19% 13% 2	1601
	11th to 20th	Day	57% 4 12% 16% 9% 1	1520
	21st to end	Day	49% 5% 18% 20% 7% 2	1520
December	1st to 10th	Day	60% 5% 15% 14% 5%	1520
	11th to 20th	Day	58% 4 17% 15% 5% 1	1915
	21st to end	Day	72% 3 8% 12% 5%	2783
January	1st to 10th	Night	63% 3 10% 18% 5% 1	4428
	11th to 20th	Night	62% 5% 12% 15% 6%	4440
	21st to end	Night	64% 3 9% 18% 5% 1	4562
February	1st to 10th	Night	51% 4 11% 23% 10% 1	2470
	11th to 20th	Night	44% 5% 15% 26% 9% 1	2404
	21st to end	Night	49% 5% 11% 22% 12% 2	1949
March	1st to 10th	Night	39% 4 13% 26% 18% 1	3582
	11th to 20th	Night	43% 4 9% 27% 16% 1	3480
	21st to end	Night	61% 3 7% 21% 8% 1	3727
April	1st to 10th	Night	48% 4 9% 22% 16% 1	1900
	11th to 20th	Night	52% 4 8% 19% 14% 2	1875
	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	36% 3 10% 33% 16% 2	2280
	11th to 20th	Night	43% 3 13% 25% 15% 2	2280
	21st to end	Night	49% 4 12% 23% 11% 1	2466
November	1st to 10th	Night	44% 4 13% 24% 15% 1	2473
	11th to 20th	Night	53% 5% 12% 17% 11% 1	2660
	21st to end	Night	49% 4 16% 23% 8% 1	2660
December	1st to 10th	Night	55% 5% 15% 19% 6%	2660
	11th to 20th	Night	59% 4 13% 17% 6% 1	3281
	21st to end	Night	67% 3 11% 15% 4	4884

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	14% 16% 30% 28% 10% 2	270
	11th to 20th	Day	17% 15% 39% 23% 5% 1	270
	21st to end	Day	13% 10% 38% 25% 11% 2	297
February	1st to 10th	Day	13% 15% 49% 16% 6% 1	270
	11th to 20th	Day	13% 21% 40% 20% 5% 1	270
	21st to end	Day	17% 17% 37% 28% 1	225
March	1st to 10th	Day	16% 15% 45% 17% 7% 1	270
	11th to 20th	Day	19% 14% 37% 21% 7% 2	270
	21st to end	Day	24% 15% 28% 21% 9% 3	348
April	1st to 10th	Day	26% 16% 31% 21% 7%	460
	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% 21% 7%	300
	21st to end	Day	26% 15% 36% 17% 6% 2	306
November	1st to 10th	Day	18% 14% 36% 20% 12% 1	270
	11th to 20th	Day	19% 17% 39% 20% 5%	270
	21st to end	Day	24% 13% 37% 20% 5%	270
December	1st to 10th	Day	14% 10% 44% 23% 7% 1	270
	11th to 20th	Day	19% 16% 38% 20% 6%	270
	21st to end	Day	26% 18% 36% 18% 2 1	297
January	1st to 10th	Night	12% 13% 36% 30% 9% 1	950
	11th to 20th	Night	16% 12% 35% 30% 6% 1	950
	21st to end	Night	18% 11% 34% 29% 7% 1	1045
February	1st to 10th	Night	11% 13% 41% 27% 7% 1	950
	11th to 20th	Night	12% 13% 41% 26% 7% 1	929
	21st to end	Night	18% 12% 32% 30% 8%	693
March	1st to 10th	Night	16% 12% 37% 26% 8% 1	674
	11th to 20th	Night	17% 12% 35% 29% 6% 1	570
	21st to end	Night	22% 10% 31% 26% 9% 2	627
April	1st to 10th	Night	21% 13% 35% 24% 6%	570
	11th to 20th	Night	26% 10% 29% 27% 7% 1	563
	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	23% 12% 27% 30% 8%	805
November	1st to 10th	Night	19% 9% 34% 29% 8% 1	807
	11th to 20th	Night	18% 13% 35% 27% 7% 1	950
	21st to end	Night	18% 14% 34% 26% 7% 1	950
December	1st to 10th	Night	17% 9% 36% 30% 7% 1	950
	11th to 20th	Night	19% 9% 39% 25% 6% 1	950
	21st to end	Night	24% 11% 35% 25% 5%	1045

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