Sayre
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Sayre clear sky chart from 2005-11-06 to 2024-04-25.

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	16% 10% 4 8% 6% 3 5% 5% 5% 7% 31%	83293
	Night	17% 10% 4 8% 6% 3 5% 5% 5% 6% 31%	85814
Transparency	Day	52% 7% 12% 19% 10% 1	83001
	Night	52% 7% 12% 19% 9% 1	85640
Seeing	Day	23% 17% 28% 19% 10% 3	13970
	Night	22% 15% 28% 25% 10% 1	23412

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	14% 17% 9% 9% 7% 3 4 4 4 5% 25%	2517
	11th to 20th	Day	12% 15% 8% 17% 8% 4 5% 4 4 6% 18%	2586
	21st to end	Day	19% 17% 8% 10% 8% 4 4 4 4 4 17%	3124
February	1st to 10th	Day	16% 14% 5% 11% 9% 4 5% 4 5% 4 23%	1710
	11th to 20th	Day	14% 11% 7% 11% 8% 4 5% 6% 4 6% 24%	1695
	21st to end	Day	20% 11% 4 11% 8% 3 3 4 5% 5% 26%	1570
March	1st to 10th	Day	24% 13% 5% 9% 6% 3 4 3 3 4 27%	3237
	11th to 20th	Day	11% 15% 5% 10% 7% 4 4 4 3 6% 32%	3480
	21st to end	Day	18% 11% 3 9% 6% 4 5% 4 5% 5% 30%	3960
April	1st to 10th	Day	18% 12% 5% 6% 5% 3 4 5% 4 5% 32%	2280
	11th to 20th	Day	18% 10% 4 7% 5% 3 5% 4 5% 7% 33%	2254
	21st to end	Day	18% 9% 4 6% 6% 3 4 4 4 7% 34%	2223
May	1st to 10th	Day	18% 10% 4 6% 6% 4 5% 5% 6% 6% 31%	2434
	11th to 20th	Day	20% 6% 2 7% 6% 3 5% 5% 5% 7% 33%	2478
	21st to end	Day	15% 6% 3 5% 6% 3 5% 5% 6% 8% 38%	2725
June	1st to 10th	Day	16% 6% 3 7% 6% 4 6% 5% 6% 8% 34%	2520
	11th to 20th	Day	15% 6% 3 6% 6% 3 5% 6% 6% 9% 35%	2520
	21st to end	Day	11% 7% 3 6% 5% 4 6% 6% 7% 10% 35%	2520
July	1st to 10th	Day	10% 5% 2 6% 6% 5% 6% 7% 7% 10% 36%	2520
	11th to 20th	Day	9% 5% 3 6% 6% 4 6% 5% 8% 9% 38%	2520
	21st to end	Day	11% 6% 3 6% 7% 4 6% 6% 7% 9% 35%	2697
August	1st to 10th	Day	10% 5% 2 6% 7% 4 8% 7% 7% 9% 35%	2327
	11th to 20th	Day	13% 7% 4 6% 7% 4 5% 6% 7% 8% 33%	2241
	21st to end	Day	14% 7% 3 6% 6% 3 6% 6% 6% 8% 34%	2376
September	1st to 10th	Day	16% 6% 3 5% 5% 3 5% 6% 5% 7% 38%	2160
	11th to 20th	Day	14% 6% 2 6% 5% 3 4 5% 5% 7% 43%	2160
	21st to end	Day	17% 7% 3 5% 5% 3 5% 5% 6% 8% 35%	1914
October	1st to 10th	Day	16% 9% 3 6% 6% 3 5% 5% 6% 8% 33%	1800
	11th to 20th	Day	18% 9% 2 8% 7% 3 4 4 5% 6% 33%	1800
	21st to end	Day	22% 11% 4 7% 7% 4 5% 5% 5% 6% 27%	1942
November	1st to 10th	Day	14% 11% 4 6% 5% 3 4 4 4 6% 38%	1671
	11th to 20th	Day	15% 12% 5% 8% 5% 4 5% 5% 5% 6% 30%	1614
	21st to end	Day	18% 12% 4 8% 7% 3 4 5% 5% 8% 26%	1520
December	1st to 10th	Day	19% 14% 6% 9% 7% 3 5% 5% 5% 7% 19%	1520
	11th to 20th	Day	21% 12% 6% 11% 6% 2 4 3 3 5% 26%	1906
	21st to end	Day	24% 19% 5% 10% 7% 4 4 4 3 5% 16%	2772
January	1st to 10th	Night	16% 13% 6% 11% 7% 3 5% 5% 5% 7% 22%	4429
	11th to 20th	Night	14% 14% 6% 13% 7% 4 4 5% 5% 6% 22%	4372
	21st to end	Night	23% 14% 6% 11% 10% 4 4 4 3 4 16%	4532
February	1st to 10th	Night	16% 12% 5% 9% 7% 4 5% 5% 5% 6% 26%	2470
	11th to 20th	Night	14% 13% 5% 10% 7% 4 6% 6% 5% 5% 25%	2370
	21st to end	Night	17% 11% 5% 11% 7% 4 5% 4 5% 5% 27%	1884
March	1st to 10th	Night	21% 14% 5% 8% 7% 3 4 3 4 4 28%	3601
	11th to 20th	Night	14% 15% 4 8% 7% 4 4 4 5% 5% 28%	3479
	21st to end	Night	16% 10% 4 9% 5% 3 4 4 5% 5% 34%	3672
April	1st to 10th	Night	19% 10% 5% 7% 5% 3 5% 3 6% 6% 31%	1900
	11th to 20th	Night	20% 9% 2 7% 6% 2 4 3 5% 6% 36%	1875
	21st to end	Night	18% 8% 3 5% 6% 3 4 4 5% 6% 37%	1850
May	1st to 10th	Night	22% 10% 3 5% 4 3 5% 5% 5% 5% 34%	1524
	11th to 20th	Night	14% 6% 3 5% 6% 5% 7% 6% 5% 8% 36%	1415
	21st to end	Night	12% 7% 3 5% 5% 3 5% 5% 6% 8% 42%	1550
June	1st to 10th	Night	15% 7% 3 6% 4 3 5% 4 5% 9% 39%	1440
	11th to 20th	Night	12% 6% 3 5% 6% 3 6% 4 6% 9% 39%	1440
	21st to end	Night	10% 4 2 5% 5% 4 5% 6% 6% 8% 44%	1440
July	1st to 10th	Night	7% 8% 3 7% 5% 3 4 6% 6% 9% 43%	1440
	11th to 20th	Night	10% 4 2 4 5% 3 5% 6% 6% 10% 45%	1440
	21st to end	Night	11% 6% 3 5% 5% 4 5% 5% 6% 9% 41%	1618
August	1st to 10th	Night	8% 5% 3 5% 6% 3 5% 6% 6% 9% 44%	1611
	11th to 20th	Night	12% 6% 2 6% 6% 4 5% 6% 7% 8% 38%	1642
	21st to end	Night	11% 6% 2 5% 6% 3 5% 5% 6% 8% 43%	1980
September	1st to 10th	Night	15% 6% 3 5% 6% 3 4 5% 4 6% 45%	1800
	11th to 20th	Night	13% 4 3 5% 4 3 4 3 5% 8% 49%	1800
	21st to end	Night	15% 7% 2 6% 5% 3 5% 4 6% 7% 41%	2044
October	1st to 10th	Night	17% 8% 3 7% 5% 2 4 4 5% 7% 38%	2160
	11th to 20th	Night	19% 8% 3 6% 5% 2 4 4 4 7% 37%	2160
	21st to end	Night	24% 11% 3 8% 5% 3 4 4 5% 6% 28%	2412
November	1st to 10th	Night	12% 10% 3 6% 5% 3 4 4 5% 7% 40%	2407
	11th to 20th	Night	18% 10% 4 6% 5% 4 5% 5% 6% 7% 31%	2565
	21st to end	Night	15% 11% 4 8% 6% 3 6% 5% 5% 7% 29%	2660
December	1st to 10th	Night	19% 12% 6% 9% 7% 3 5% 5% 6% 7% 22%	2660
	11th to 20th	Night	20% 12% 5% 10% 6% 3 4 5% 4 6% 24%	3288
	21st to end	Night	25% 16% 4 8% 6% 3 4 5% 5% 5% 19%	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	62% 5% 10% 19% 4 1	2518
	11th to 20th	Day	68% 5% 10% 12% 5% 1	2586
	21st to end	Day	70% 5% 10% 11% 3	3124
February	1st to 10th	Day	64% 5% 11% 13% 7% 1	1710
	11th to 20th	Day	61% 6% 8% 18% 7%	1704
	21st to end	Day	60% 5% 10% 16% 8% 1	1570
March	1st to 10th	Day	62% 3 9% 19% 5% 1	3240
	11th to 20th	Day	52% 6% 12% 19% 9% 2	3480
	21st to end	Day	54% 5% 8% 18% 13% 1	3960
April	1st to 10th	Day	54% 5% 8% 21% 10% 2	2280
	11th to 20th	Day	50% 6% 11% 19% 13% 1	2254
	21st to end	Day	50% 5% 10% 20% 12% 3	2223
May	1st to 10th	Day	52% 7% 9% 19% 11% 2	2434
	11th to 20th	Day	49% 7% 9% 20% 13% 2	2482
	21st to end	Day	43% 9% 14% 21% 12% 1	2725
June	1st to 10th	Day	47% 8% 11% 20% 13% 1	2520
	11th to 20th	Day	44% 9% 14% 21% 11% 1	2520
	21st to end	Day	41% 9% 13% 23% 12% 1	2520
July	1st to 10th	Day	41% 9% 15% 21% 12% 2	2450
	11th to 20th	Day	38% 9% 16% 23% 13% 1	2445
	21st to end	Day	43% 8% 14% 20% 14% 1	2546
August	1st to 10th	Day	42% 9% 15% 22% 11%	2314
	11th to 20th	Day	45% 10% 13% 23% 9% 1	2241
	21st to end	Day	45% 7% 12% 22% 12% 2	2376
September	1st to 10th	Day	43% 6% 13% 24% 12% 2	2160
	11th to 20th	Day	40% 6% 11% 23% 19% 1	2160
	21st to end	Day	45% 5% 13% 22% 12% 2	1914
October	1st to 10th	Day	47% 9% 12% 20% 13% 1	1800
	11th to 20th	Day	51% 6% 11% 22% 10%	1800
	21st to end	Day	58% 6% 12% 15% 8% 1	1942
November	1st to 10th	Day	46% 6% 13% 21% 12% 2	1671
	11th to 20th	Day	53% 6% 11% 20% 9% 2	1614
	21st to end	Day	57% 6% 14% 18% 6%	1520
December	1st to 10th	Day	63% 9% 12% 12% 5%	1520
	11th to 20th	Day	62% 5% 16% 12% 4	1906
	21st to end	Day	72% 6% 9% 11% 3	2772
January	1st to 10th	Night	61% 6% 12% 15% 6% 1	4429
	11th to 20th	Night	61% 6% 13% 15% 4	4372
	21st to end	Night	73% 4 7% 11% 4	4532
February	1st to 10th	Night	57% 6% 13% 16% 8%	2470
	11th to 20th	Night	59% 7% 11% 15% 7% 1	2372
	21st to end	Night	58% 5% 11% 15% 9% 2	1884
March	1st to 10th	Night	60% 5% 10% 17% 7% 1	3611
	11th to 20th	Night	55% 7% 13% 19% 6% 1	3480
	21st to end	Night	50% 5% 11% 21% 12% 3	3672
April	1st to 10th	Night	54% 5% 10% 18% 11% 1	1900
	11th to 20th	Night	49% 5% 12% 19% 15% 1	1875
	21st to end	Night	47% 6% 11% 19% 15% 3	1850
May	1st to 10th	Night	51% 6% 9% 20% 10% 3	1524
	11th to 20th	Night	45% 8% 12% 19% 15% 2	1416
	21st to end	Night	39% 9% 14% 23% 13% 2	1551
June	1st to 10th	Night	42% 7% 12% 24% 15%	1440
	11th to 20th	Night	41% 8% 14% 24% 12% 2	1440
	21st to end	Night	36% 8% 14% 27% 14% 1	1440
July	1st to 10th	Night	36% 8% 15% 25% 14% 2	1400
	11th to 20th	Night	32% 9% 17% 26% 17% 1	1392
	21st to end	Night	38% 9% 15% 20% 16% 2	1528
August	1st to 10th	Night	34% 8% 18% 27% 11% 1	1600
	11th to 20th	Night	42% 10% 14% 25% 11%	1642
	21st to end	Night	37% 8% 14% 25% 15% 1	1980
September	1st to 10th	Night	41% 5% 13% 26% 13% 2	1800
	11th to 20th	Night	34% 6% 13% 27% 18% 1	1800
	21st to end	Night	42% 7% 11% 24% 15% 1	2044
October	1st to 10th	Night	45% 7% 14% 21% 13% 1	2160
	11th to 20th	Night	46% 6% 14% 21% 11% 1	2160
	21st to end	Night	56% 5% 12% 17% 9% 1	2412
November	1st to 10th	Night	44% 6% 14% 21% 14% 2	2407
	11th to 20th	Night	51% 7% 13% 19% 9% 2	2565
	21st to end	Night	52% 7% 16% 20% 5%	2660
December	1st to 10th	Night	60% 8% 14% 14% 4	2660
	11th to 20th	Night	61% 6% 12% 15% 6%	3288
	21st to end	Night	66% 7% 11% 14% 2	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	31% 18% 37% 9% 4 1	180
	11th to 20th	Day	37% 28% 26% 8% 1 1	200
	21st to end	Day	25% 30% 31% 11% 2 1	297
February	1st to 10th	Day	32% 32% 28% 7% 1	270
	11th to 20th	Day	36% 30% 29% 4 1	302
	21st to end	Day	35% 25% 28% 11% 2	382
March	1st to 10th	Day	33% 22% 28% 14% 4	460
	11th to 20th	Day	31% 25% 27% 12% 5% 1	460
	21st to end	Day	31% 25% 25% 12% 4 2	506
April	1st to 10th	Day	31% 22% 27% 16% 3 1	460
	11th to 20th	Day	26% 26% 27% 11% 7% 3	452
	21st to end	Day	29% 20% 29% 14% 6% 2	437
May	1st to 10th	Day	29% 17% 32% 12% 6% 4	423
	11th to 20th	Day	21% 15% 31% 19% 11% 3	447
	21st to end	Day	21% 10% 29% 21% 14% 5%	485
June	1st to 10th	Day	17% 16% 31% 22% 11% 2	450
	11th to 20th	Day	19% 13% 27% 26% 13% 1	450
	21st to end	Day	13% 14% 36% 23% 10% 3	450
July	1st to 10th	Day	12% 8% 27% 29% 18% 6%	445
	11th to 20th	Day	7% 7% 29% 31% 21% 4	444
	21st to end	Day	13% 9% 33% 27% 14% 4	488
August	1st to 10th	Day	12% 8% 26% 26% 20% 8%	446
	11th to 20th	Day	15% 8% 27% 28% 14% 9%	439
	21st to end	Day	13% 11% 26% 25% 14% 11%	495
September	1st to 10th	Day	18% 11% 23% 23% 16% 9%	450
	11th to 20th	Day	17% 8% 23% 23% 18% 10%	450
	21st to end	Day	20% 12% 28% 20% 14% 5%	450
October	1st to 10th	Day	23% 11% 24% 22% 14% 5%	450
	11th to 20th	Day	24% 18% 29% 22% 7% 1	450
	21st to end	Day	31% 19% 28% 16% 6%	475
November	1st to 10th	Day	23% 19% 25% 20% 12% 1	365
	11th to 20th	Day	29% 20% 27% 19% 5%	274
	21st to end	Day	32% 26% 30% 10% 2	180
December	1st to 10th	Day	33% 23% 28% 11% 4 1	180
	11th to 20th	Day	36% 23% 29% 10% 2	180
	21st to end	Day	38% 22% 29% 10% 2	198
January	1st to 10th	Night	22% 24% 35% 16% 3	760
	11th to 20th	Night	26% 20% 30% 21% 3	760
	21st to end	Night	22% 22% 33% 19% 3	836
February	1st to 10th	Night	25% 20% 32% 21% 1	760
	11th to 20th	Night	27% 23% 33% 15% 1	743
	21st to end	Night	28% 23% 29% 17% 3	628
March	1st to 10th	Night	25% 23% 28% 21% 3	760
	11th to 20th	Night	28% 21% 29% 19% 4	760
	21st to end	Night	25% 21% 29% 19% 6% 1	836
April	1st to 10th	Night	26% 19% 31% 20% 4	760
	11th to 20th	Night	26% 19% 27% 20% 7% 1	751
	21st to end	Night	22% 16% 30% 26% 7%	740
May	1st to 10th	Night	27% 9% 25% 29% 9% 1	444
	11th to 20th	Night	16% 10% 32% 33% 9% 1	354
	21st to end	Night	14% 9% 27% 33% 16%	389
June	1st to 10th	Night	16% 8% 24% 36% 15% 1	360
	11th to 20th	Night	14% 9% 24% 36% 17%	360
	21st to end	Night	11% 4 26% 44% 14% 1	360
July	1st to 10th	Night	9% 4 22% 43% 20% 2	350
	11th to 20th	Night	10% 4 20% 46% 19% 2	348
	21st to end	Night	15% 4 17% 44% 19% 1	438
August	1st to 10th	Night	11% 2 19% 39% 27% 2	537
	11th to 20th	Night	14% 4 16% 36% 27% 3	578
	21st to end	Night	11% 6% 20% 36% 25% 2	792
September	1st to 10th	Night	16% 6% 24% 34% 18% 2	720
	11th to 20th	Night	13% 7% 20% 29% 26% 4	720
	21st to end	Night	15% 10% 25% 29% 18% 2	720
October	1st to 10th	Night	22% 8% 25% 26% 18% 2	720
	11th to 20th	Night	24% 12% 27% 28% 8% 1	720
	21st to end	Night	31% 14% 28% 22% 4	792
November	1st to 10th	Night	19% 17% 29% 28% 8% 1	740
	11th to 20th	Night	25% 18% 31% 18% 7% 1	760
	21st to end	Night	24% 17% 32% 22% 5% 1	760
December	1st to 10th	Night	28% 21% 29% 18% 4	760
	11th to 20th	Night	27% 20% 29% 21% 3	760
	21st to end	Night	28% 19% 33% 18% 2	836

Page generated at 2024-04-22 09:25:39. Version ac07

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