Midland
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Midland clear sky chart from 2005-11-06 to 2025-02-25.

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	15% 11% 4 9% 5% 5% 4 3 5% 6% 32%	109080
	Night	15% 14% 5% 11% 6% 5% 4 3 5% 5% 27%	109581
Transparency	Day	51% 7% 12% 20% 10% 1	112697
	Night	56% 7% 11% 17% 9% 1	114128
Seeing	Day	22% 16% 30% 20% 9% 3	15242
	Night	23% 16% 28% 23% 9% 1	24378

By Month

Percentage Cloud Cover NE (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	13% 16% 10% 14% 6% 7% 5% 4 4 4 16%	3260
	11th to 20th	Day	9% 18% 9% 21% 10% 9% 6% 3 3 4 9%	3860
	21st to end	Day	12% 18% 9% 17% 7% 7% 6% 3 5% 4 13%	4466
February	1st to 10th	Day	13% 18% 7% 18% 9% 4 4 3 3 5% 17%	1800
	11th to 20th	Day	13% 16% 7% 15% 7% 5% 4 3 4 5% 22%	1753
	21st to end	Day	16% 17% 7% 11% 6% 6% 5% 3 4 4 21%	1494
March	1st to 10th	Day	17% 13% 5% 9% 6% 5% 4 3 4 5% 30%	3419
	11th to 20th	Day	12% 17% 5% 10% 6% 5% 5% 3 5% 5% 27%	3480
	21st to end	Day	15% 11% 5% 8% 6% 4 4 3 5% 6% 34%	3815
April	1st to 10th	Day	20% 13% 5% 8% 4 4 4 2 4 5% 31%	2232
	11th to 20th	Day	20% 12% 3 6% 4 4 4 3 5% 5% 36%	2375
	21st to end	Day	21% 10% 3 6% 4 3 4 3 4 5% 36%	2470
May	1st to 10th	Day	19% 8% 3 6% 4 4 4 3 5% 7% 37%	4108
	11th to 20th	Day	14% 8% 2 7% 4 4 4 4 6% 8% 39%	4396
	21st to end	Day	15% 7% 2 5% 4 4 4 4 6% 7% 44%	4837
June	1st to 10th	Day	18% 7% 2 6% 4 4 4 4 5% 6% 39%	2669
	11th to 20th	Day	12% 6% 2 6% 4 4 5% 4 6% 9% 42%	2850
	21st to end	Day	17% 7% 2 5% 4 4 4 3 6% 7% 41%	2850
July	1st to 10th	Day	13% 6% 2 7% 5% 4 5% 4 7% 9% 39%	4760
	11th to 20th	Day	13% 6% 2 5% 4 3 3 4 5% 7% 48%	4541
	21st to end	Day	10% 5% 2 6% 4 4 4 4 6% 8% 49%	4543
August	1st to 10th	Day	15% 6% 2 6% 5% 4 5% 3 6% 8% 41%	4104
	11th to 20th	Day	15% 6% 3 5% 4 4 4 4 6% 9% 39%	4044
	21st to end	Day	10% 5% 2 5% 4 5% 5% 4 6% 8% 46%	4414
September	1st to 10th	Day	15% 7% 2 7% 4 4 4 3 5% 7% 42%	2280
	11th to 20th	Day	13% 6% 3 5% 4 4 4 3 5% 8% 46%	2147
	21st to end	Day	17% 8% 2 7% 6% 5% 5% 3 5% 5% 37%	2066
October	1st to 10th	Day	21% 8% 3 7% 4 3 4 3 5% 6% 34%	1900
	11th to 20th	Day	23% 13% 4 10% 4 6% 4 3 4 6% 23%	1900
	21st to end	Day	29% 15% 5% 9% 4 4 4 3 4 5% 18%	2084
November	1st to 10th	Day	18% 18% 5% 9% 5% 4 4 3 4 7% 24%	1637
	11th to 20th	Day	19% 18% 5% 10% 6% 6% 5% 3 5% 6% 18%	1600
	21st to end	Day	20% 25% 5% 11% 6% 5% 5% 4 4 5% 11%	1600
December	1st to 10th	Day	18% 26% 8% 15% 7% 5% 4 2 4 3 7%	2600
	11th to 20th	Day	17% 22% 9% 15% 6% 4 3 3 4 4 13%	2986
	21st to end	Day	22% 19% 7% 14% 6% 5% 5% 3 4 4 13%	3740
January	1st to 10th	Night	12% 22% 11% 17% 7% 5% 4 3 4 3 11%	6691
	11th to 20th	Night	11% 15% 9% 20% 11% 7% 5% 3 5% 4 9%	6023
	21st to end	Night	13% 16% 9% 14% 8% 7% 5% 4 5% 5% 15%	6490
February	1st to 10th	Night	12% 20% 7% 17% 8% 5% 4 3 4 4 16%	2600
	11th to 20th	Night	13% 18% 7% 14% 7% 5% 4 2 5% 4 21%	2533
	21st to end	Night	17% 15% 5% 11% 7% 5% 4 3 4 6% 23%	2053
March	1st to 10th	Night	15% 12% 5% 9% 5% 4 4 3 5% 6% 31%	3420
	11th to 20th	Night	12% 17% 6% 8% 5% 4 3 3 5% 6% 30%	3479
	21st to end	Night	14% 11% 6% 11% 6% 5% 5% 4 4 5% 29%	3817
April	1st to 10th	Night	21% 12% 3 8% 5% 4 3 3 5% 5% 30%	1947
	11th to 20th	Night	19% 10% 3 6% 5% 4 4 3 5% 5% 36%	1770
	21st to end	Night	18% 10% 4 9% 5% 4 4 3 5% 6% 32%	1710
May	1st to 10th	Night	16% 7% 2 7% 4 5% 4 4 6% 7% 39%	2833
	11th to 20th	Night	16% 8% 2 6% 4 4 4 4 5% 7% 40%	2495
	21st to end	Night	11% 7% 2 6% 4 4 3 4 5% 8% 47%	2738
June	1st to 10th	Night	16% 8% 2 6% 5% 4 5% 4 7% 7% 36%	1506
	11th to 20th	Night	12% 5% 1 5% 4 4 5% 5% 6% 11% 42%	1330
	21st to end	Night	15% 7% 3 7% 3 5% 4 3 7% 7% 40%	1330
July	1st to 10th	Night	9% 6% 2 8% 5% 4 4 3 6% 6% 47%	2210
	11th to 20th	Night	15% 5% 2 5% 4 3 3 2 5% 6% 50%	2417
	21st to end	Night	9% 5% 2 5% 5% 4 4 4 5% 8% 49%	3006
August	1st to 10th	Night	11% 5% 3 5% 4 4 5% 4 6% 7% 46%	2825
	11th to 20th	Night	16% 7% 2 6% 3 3 4 3 5% 6% 45%	2785
	21st to end	Night	15% 6% 2 5% 4 3 4 3 5% 7% 47%	3210
September	1st to 10th	Night	12% 5% 2 6% 5% 3 4 4 6% 8% 45%	1900
	11th to 20th	Night	14% 6% 2 5% 4 4 4 3 4 6% 48%	2029
	21st to end	Night	17% 7% 3 7% 4 5% 4 3 5% 6% 40%	2114
October	1st to 10th	Night	20% 7% 3 8% 5% 4 4 3 4 5% 37%	2280
	11th to 20th	Night	24% 12% 3 8% 4 4 5% 3 4 6% 26%	2280
	21st to end	Night	25% 15% 4 10% 5% 5% 4 3 5% 5% 20%	2513
November	1st to 10th	Night	20% 15% 4 8% 6% 4 3 3 4 5% 27%	2661
	11th to 20th	Night	18% 20% 6% 10% 6% 5% 4 3 5% 5% 20%	2800
	21st to end	Night	21% 23% 7% 10% 6% 5% 4 3 4 5% 13%	2800
December	1st to 10th	Night	18% 28% 8% 15% 5% 4 4 3 4 3 7%	4580
	11th to 20th	Night	14% 23% 9% 18% 6% 5% 4 3 4 4 10%	5208
	21st to end	Night	21% 22% 7% 15% 6% 4 3 3 3 4 12%	7198

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% 9% 13% 9% 5%	3261
	11th to 20th	Day	74% 11% 5% 6% 3	3894
	21st to end	Day	71% 8% 8% 7% 5%	4466
February	1st to 10th	Day	71% 4 8% 13% 3	1800
	11th to 20th	Day	65% 5% 9% 13% 7% 1	1762
	21st to end	Day	66% 5% 9% 14% 5%	1494
March	1st to 10th	Day	56% 6% 15% 13% 10%	3422
	11th to 20th	Day	59% 5% 13% 16% 6% 1	3480
	21st to end	Day	48% 5% 13% 19% 12% 2	3815
April	1st to 10th	Day	56% 4 10% 18% 10% 1	2232
	11th to 20th	Day	50% 4 9% 23% 13% 1	2375
	21st to end	Day	51% 5% 10% 20% 12% 3	2470
May	1st to 10th	Day	46% 6% 13% 20% 14% 2	4120
	11th to 20th	Day	42% 8% 15% 24% 11% 1	4400
	21st to end	Day	38% 8% 12% 21% 17% 3	4837
June	1st to 10th	Day	44% 7% 11% 24% 14%	2669
	11th to 20th	Day	37% 8% 13% 25% 16% 1	2850
	21st to end	Day	42% 7% 13% 23% 14% 1	2850
July	1st to 10th	Day	40% 8% 16% 23% 13% 1	4686
	11th to 20th	Day	34% 6% 14% 35% 10% 1	4462
	21st to end	Day	34% 6% 11% 28% 19% 1	4398
August	1st to 10th	Day	41% 7% 15% 24% 12% 1	4091
	11th to 20th	Day	40% 7% 18% 26% 10%	4083
	21st to end	Day	34% 7% 14% 34% 10% 1	4414
September	1st to 10th	Day	41% 6% 13% 27% 11% 1	2280
	11th to 20th	Day	37% 7% 14% 29% 12%	2147
	21st to end	Day	48% 7% 12% 24% 8%	2066
October	1st to 10th	Day	45% 6% 13% 26% 10%	3160
	11th to 20th	Day	52% 6% 13% 21% 9%	3140
	21st to end	Day	62% 8% 12% 15% 4	3410
November	1st to 10th	Day	61% 6% 10% 17% 5%	1637
	11th to 20th	Day	66% 8% 11% 10% 4 1	1600
	21st to end	Day	76% 8% 7% 8% 1	1600
December	1st to 10th	Day	80% 7% 8% 5% 1	2600
	11th to 20th	Day	74% 6% 8% 10% 2	2986
	21st to end	Day	74% 6% 7% 8% 5%	3740
January	1st to 10th	Night	74% 6% 7% 9% 3	6691
	11th to 20th	Night	71% 11% 6% 7% 4	6064
	21st to end	Night	68% 8% 10% 8% 6% 1	6490
February	1st to 10th	Night	71% 5% 8% 12% 3	2600
	11th to 20th	Night	66% 4 9% 14% 6%	2535
	21st to end	Night	63% 6% 10% 15% 6%	2053
March	1st to 10th	Night	53% 5% 14% 17% 10% 1	3430
	11th to 20th	Night	55% 6% 13% 17% 9% 1	3480
	21st to end	Night	53% 6% 11% 18% 10% 1	3817
April	1st to 10th	Night	56% 4 9% 19% 11% 1	1947
	11th to 20th	Night	50% 4 7% 21% 16% 2	1770
	21st to end	Night	52% 6% 10% 14% 16% 1	1710
May	1st to 10th	Night	43% 7% 13% 21% 15% 2	2840
	11th to 20th	Night	42% 8% 10% 23% 15% 2	2496
	21st to end	Night	35% 8% 12% 26% 18% 2	2739
June	1st to 10th	Night	44% 7% 11% 21% 16% 1	1506
	11th to 20th	Night	34% 7% 12% 26% 20% 1	1330
	21st to end	Night	42% 8% 13% 24% 13% 1	1330
July	1st to 10th	Night	37% 6% 13% 24% 17% 3	2175
	11th to 20th	Night	35% 5% 12% 34% 14% 1	2373
	21st to end	Night	33% 7% 12% 30% 17% 1	2910
August	1st to 10th	Night	37% 6% 14% 27% 16% 1	2814
	11th to 20th	Night	39% 6% 17% 24% 13% 1	2812
	21st to end	Night	37% 6% 11% 33% 13% 1	3210
September	1st to 10th	Night	36% 7% 14% 28% 13% 1	1900
	11th to 20th	Night	37% 7% 13% 29% 15%	2029
	21st to end	Night	44% 6% 14% 25% 10%	2114
October	1st to 10th	Night	38% 6% 10% 27% 18%	3800
	11th to 20th	Night	50% 6% 15% 20% 10%	3779
	21st to end	Night	54% 7% 15% 20% 5%	4137
November	1st to 10th	Night	59% 6% 10% 18% 7%	2661
	11th to 20th	Night	65% 7% 12% 11% 4 1	2800
	21st to end	Night	73% 8% 10% 8% 2	2800
December	1st to 10th	Night	79% 7% 9% 4 1	4580
	11th to 20th	Night	78% 7% 8% 6% 1	5208
	21st to end	Night	77% 5% 6% 8% 4	7198

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	20% 31% 33% 12% 5% 1	200
	11th to 20th	Day	21% 27% 34% 12% 5%	263
	21st to end	Day	27% 22% 31% 18% 2	330
February	1st to 10th	Day	29% 30% 29% 10% 2	300
	11th to 20th	Day	26% 28% 38% 7% 1	300
	21st to end	Day	33% 30% 29% 8%	237
March	1st to 10th	Day	22% 23% 38% 14% 4	447
	11th to 20th	Day	24% 20% 35% 17% 4 1	460
	21st to end	Day	29% 20% 28% 16% 6%	506
April	1st to 10th	Day	27% 22% 30% 15% 7% 1	460
	11th to 20th	Day	35% 19% 22% 15% 6% 3	452
	21st to end	Day	30% 18% 32% 14% 5% 2	460
May	1st to 10th	Day	26% 11% 33% 19% 7% 4	463
	11th to 20th	Day	18% 13% 28% 25% 13% 3	487
	21st to end	Day	17% 12% 29% 26% 10% 5%	529
June	1st to 10th	Day	23% 10% 28% 27% 10% 1	499
	11th to 20th	Day	15% 13% 31% 27% 11% 3	680
	21st to end	Day	21% 10% 32% 24% 11% 2	680
July	1st to 10th	Day	11% 9% 30% 29% 17% 3	671
	11th to 20th	Day	15% 10% 28% 28% 14% 5%	542
	21st to end	Day	11% 8% 33% 30% 12% 6%	532
August	1st to 10th	Day	14% 7% 27% 29% 15% 8%	486
	11th to 20th	Day	15% 8% 24% 28% 16% 9%	479
	21st to end	Day	13% 11% 31% 26% 14% 6%	539
September	1st to 10th	Day	17% 10% 25% 27% 14% 7%	490
	11th to 20th	Day	13% 7% 28% 22% 19% 11%	490
	21st to end	Day	17% 16% 24% 27% 11% 5%	490
October	1st to 10th	Day	24% 17% 28% 16% 12% 3	490
	11th to 20th	Day	25% 22% 32% 15% 6%	490
	21st to end	Day	36% 19% 29% 12% 4	533
November	1st to 10th	Day	31% 22% 27% 16% 3	237
	11th to 20th	Day	31% 24% 33% 11% 2 1	200
	21st to end	Day	29% 26% 36% 10%	200
December	1st to 10th	Day	30% 29% 25% 14% 2 1	200
	11th to 20th	Day	31% 35% 22% 11% 2 1	200
	21st to end	Day	35% 24% 29% 10% 2	220
January	1st to 10th	Night	26% 26% 31% 12% 5%	948
	11th to 20th	Night	31% 20% 29% 17% 3 1	800
	21st to end	Night	22% 16% 32% 22% 6% 1	880
February	1st to 10th	Night	25% 23% 32% 18% 2	800
	11th to 20th	Night	23% 21% 32% 19% 5%	783
	21st to end	Night	27% 21% 30% 18% 4	647
March	1st to 10th	Night	22% 19% 34% 21% 4	760
	11th to 20th	Night	23% 21% 32% 19% 5% 1	760
	21st to end	Night	22% 15% 31% 25% 7%	836
April	1st to 10th	Night	29% 13% 33% 23% 3	760
	11th to 20th	Night	25% 16% 28% 20% 11%	646
	21st to end	Night	22% 12% 32% 21% 12%	570
May	1st to 10th	Night	20% 9% 23% 34% 12% 1	570
	11th to 20th	Night	18% 9% 26% 33% 12% 1	374
	21st to end	Night	12% 7% 29% 37% 15%	411
June	1st to 10th	Night	17% 8% 30% 32% 12% 1	380
	11th to 20th	Night	13% 9% 26% 37% 16%	380
	21st to end	Night	16% 6% 28% 33% 16% 1	380
July	1st to 10th	Night	9% 8% 17% 45% 20% 1	370
	11th to 20th	Night	10% 8% 30% 29% 22% 2	368
	21st to end	Night	11% 5% 26% 36% 21% 1	569
August	1st to 10th	Night	11% 5% 22% 34% 25% 3	567
	11th to 20th	Night	10% 7% 21% 35% 24% 4	564
	21st to end	Night	17% 7% 23% 28% 23% 2	674
September	1st to 10th	Night	13% 8% 28% 28% 18% 4	760
	11th to 20th	Night	15% 8% 22% 31% 19% 5%	760
	21st to end	Night	20% 11% 22% 30% 14% 4	760
October	1st to 10th	Night	23% 13% 29% 21% 13% 1	760
	11th to 20th	Night	31% 18% 24% 18% 8% 1	760
	21st to end	Night	31% 20% 28% 16% 4	836
November	1st to 10th	Night	30% 18% 28% 17% 6% 1	780
	11th to 20th	Night	27% 24% 29% 15% 5%	800
	21st to end	Night	35% 20% 29% 14% 3 1	800
December	1st to 10th	Night	34% 27% 25% 11% 3	800
	11th to 20th	Night	28% 25% 32% 11% 3 1	800
	21st to end	Night	33% 21% 29% 15% 2	965

Page generated at 2025-02-22 06:51:37. Version ac07

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