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 2025-10-19.

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 9% 5% 5% 5% 4 5% 7% 30%	126943
	Night	16% 11% 4 9% 5% 5% 4 4 5% 6% 31%	122737
Transparency	Day	51% 6% 12% 20% 10% 1	130486
	Night	51% 6% 12% 19% 10% 1	127280
Seeing	Day	23% 17% 28% 19% 10% 3	15960
	Night	22% 15% 27% 25% 10% 1	25189

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	12% 15% 10% 19% 7% 3 3 2 4 5% 18%	3597
	11th to 20th	Day	12% 14% 7% 21% 7% 5% 4 3 4 5% 16%	3678
	21st to end	Day	16% 15% 7% 10% 6% 5% 4 4 4 5% 24%	4466
February	1st to 10th	Day	16% 15% 4 12% 8% 6% 5% 3 5% 4 23%	1800
	11th to 20th	Day	14% 13% 6% 13% 7% 5% 5% 4 4 6% 23%	1787
	21st to end	Day	19% 12% 3 11% 7% 4 3 3 5% 5% 26%	1650
March	1st to 10th	Day	20% 13% 5% 10% 6% 4 4 3 3 4 29%	4653
	11th to 20th	Day	12% 14% 3 9% 5% 4 4 3 4 6% 37%	4980
	21st to end	Day	15% 11% 4 11% 6% 6% 5% 4 5% 5% 29%	5666
April	1st to 10th	Day	18% 14% 4 8% 5% 4 4 3 5% 5% 31%	2400
	11th to 20th	Day	17% 11% 3 8% 4 4 4 4 5% 7% 32%	2374
	21st to end	Day	17% 10% 3 8% 5% 4 4 3 5% 6% 35%	2415
May	1st to 10th	Day	28% 10% 3 6% 4 4 4 3 5% 6% 26%	6136
	11th to 20th	Day	19% 10% 3 9% 5% 4 5% 4 5% 7% 28%	6318
	21st to end	Day	20% 8% 3 7% 4 4 5% 4 6% 8% 31%	6949
June	1st to 10th	Day	16% 7% 3 7% 5% 5% 5% 4 6% 8% 33%	2800
	11th to 20th	Day	15% 7% 2 7% 5% 5% 5% 4 7% 9% 34%	2800
	21st to end	Day	11% 7% 3 7% 4 6% 5% 5% 7% 10% 35%	2800
July	1st to 10th	Day	8% 6% 3 7% 5% 6% 6% 5% 8% 10% 37%	6360
	11th to 20th	Day	6% 6% 3 9% 7% 6% 7% 5% 9% 10% 31%	6360
	21st to end	Day	11% 6% 2 7% 5% 5% 5% 5% 6% 8% 39%	6798
August	1st to 10th	Day	17% 8% 3 8% 5% 5% 6% 4 6% 8% 31%	4234
	11th to 20th	Day	15% 8% 3 7% 5% 4 6% 5% 7% 10% 30%	4052
	21st to end	Day	14% 8% 3 6% 4 4 5% 4 7% 8% 38%	4312
September	1st to 10th	Day	15% 6% 3 6% 4 4 5% 4 6% 8% 41%	2400
	11th to 20th	Day	13% 6% 2 6% 4 4 5% 4 5% 7% 43%	2400
	21st to end	Day	19% 8% 3 7% 5% 4 5% 4 6% 8% 32%	2124
October	1st to 10th	Day	15% 8% 3 7% 5% 4 4 4 6% 8% 35%	2000
	11th to 20th	Day	18% 9% 2 9% 5% 5% 4 3 5% 6% 34%	1980
	21st to end	Day	20% 11% 3 8% 5% 5% 4 4 5% 6% 28%	2049
November	1st to 10th	Day	14% 12% 3 7% 4 4 4 4 4 6% 38%	1761
	11th to 20th	Day	15% 14% 4 9% 4 5% 5% 4 5% 6% 30%	1698
	21st to end	Day	18% 14% 5% 8% 6% 5% 4 3 5% 8% 25%	1600
December	1st to 10th	Day	16% 16% 6% 14% 7% 6% 5% 4 4 6% 17%	2600
	11th to 20th	Day	20% 13% 6% 11% 6% 3 4 3 3 4 27%	2986
	21st to end	Day	19% 16% 5% 14% 6% 5% 4 3 4 6% 16%	3960
January	1st to 10th	Night	13% 12% 6% 19% 7% 5% 5% 4 5% 6% 19%	6349
	11th to 20th	Night	11% 13% 6% 16% 6% 6% 5% 4 6% 6% 20%	6205
	21st to end	Night	18% 13% 5% 13% 8% 6% 5% 4 4 5% 21%	6490
February	1st to 10th	Night	16% 13% 5% 9% 7% 5% 5% 4 5% 6% 26%	2600
	11th to 20th	Night	14% 14% 4 12% 6% 6% 5% 5% 5% 5% 24%	2498
	21st to end	Night	17% 12% 5% 12% 6% 5% 5% 3 5% 5% 26%	1980
March	1st to 10th	Night	17% 12% 6% 10% 7% 4 4 3 4 4 29%	5185
	11th to 20th	Night	14% 13% 4 8% 5% 4 4 3 5% 5% 36%	4979
	21st to end	Night	16% 11% 4 11% 5% 5% 4 4 5% 6% 30%	5252
April	1st to 10th	Night	19% 12% 4 8% 5% 5% 4 3 5% 6% 29%	2000
	11th to 20th	Night	20% 11% 2 7% 5% 3 3 3 5% 6% 35%	1975
	21st to end	Night	17% 9% 3 6% 5% 4 4 3 6% 6% 38%	2000
May	1st to 10th	Night	31% 9% 3 6% 4 4 4 3 4 5% 26%	3789
	11th to 20th	Night	20% 10% 3 7% 4 4 4 4 5% 7% 33%	3575
	21st to end	Night	18% 9% 3 8% 5% 5% 5% 4 6% 7% 31%	3926
June	1st to 10th	Night	15% 8% 3 7% 4 4 5% 4 5% 9% 38%	1600
	11th to 20th	Night	13% 7% 3 6% 5% 4 5% 4 6% 8% 39%	1600
	21st to end	Night	11% 5% 2 6% 5% 6% 5% 4 6% 8% 43%	1600
July	1st to 10th	Night	8% 8% 3 9% 5% 5% 5% 4 5% 10% 38%	3600
	11th to 20th	Night	10% 5% 2 7% 5% 6% 6% 5% 6% 11% 37%	3600
	21st to end	Night	10% 6% 2 6% 4 5% 4 3 5% 8% 46%	4051
August	1st to 10th	Night	18% 6% 3 7% 5% 4 5% 4 6% 7% 35%	2915
	11th to 20th	Night	15% 8% 3 6% 4 4 4 3 5% 6% 41%	2964
	21st to end	Night	12% 7% 2 5% 5% 5% 5% 4 6% 8% 42%	3586
September	1st to 10th	Night	14% 6% 2 6% 5% 4 4 3 4 6% 46%	2000
	11th to 20th	Night	12% 5% 2 5% 3 4 4 3 5% 8% 49%	2000
	21st to end	Night	17% 8% 2 7% 4 5% 4 3 6% 7% 38%	2273
October	1st to 10th	Night	16% 8% 3 7% 4 3 4 3 5% 7% 39%	2400
	11th to 20th	Night	19% 8% 2 7% 4 3 4 3 5% 7% 38%	2377
	21st to end	Night	22% 11% 3 8% 4 4 4 3 5% 6% 30%	2547
November	1st to 10th	Night	12% 10% 3 7% 4 4 4 3 5% 7% 41%	2537
	11th to 20th	Night	18% 11% 3 7% 5% 5% 4 4 6% 6% 32%	2700
	21st to end	Night	15% 12% 4 9% 6% 4 5% 4 6% 7% 29%	2800
December	1st to 10th	Night	13% 12% 6% 13% 6% 6% 5% 4 6% 7% 21%	4580
	11th to 20th	Night	21% 13% 4 9% 5% 3 4 3 5% 5% 27%	5208
	21st to end	Night	21% 17% 5% 10% 6% 5% 4 4 5% 5% 19%	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	68% 4 8% 16% 3 1	3598
	11th to 20th	Day	70% 4 8% 11% 6% 1	3708
	21st to end	Day	61% 5% 10% 16% 8%	4466
February	1st to 10th	Day	64% 5% 10% 13% 7% 1	1800
	11th to 20th	Day	62% 6% 7% 18% 7%	1796
	21st to end	Day	59% 5% 10% 17% 8% 1	1650
March	1st to 10th	Day	59% 4 10% 18% 9% 1	4656
	11th to 20th	Day	48% 5% 18% 19% 9% 2	4980
	21st to end	Day	55% 5% 8% 15% 14% 2	5666
April	1st to 10th	Day	55% 5% 8% 21% 10% 2	2400
	11th to 20th	Day	50% 6% 11% 18% 14% 1	2374
	21st to end	Day	49% 5% 10% 20% 13% 3	2415
May	1st to 10th	Day	59% 6% 9% 15% 10% 1	6145
	11th to 20th	Day	54% 8% 8% 19% 10% 1	6322
	21st to end	Day	48% 8% 12% 20% 11% 1	6949
June	1st to 10th	Day	46% 8% 11% 20% 14% 1	2800
	11th to 20th	Day	44% 8% 14% 21% 11% 1	2800
	21st to end	Day	42% 9% 14% 22% 12% 1	2800
July	1st to 10th	Day	39% 8% 16% 25% 12% 1	6290
	11th to 20th	Day	40% 10% 17% 22% 11%	6285
	21st to end	Day	40% 7% 13% 23% 17% 1	6602
August	1st to 10th	Day	49% 8% 14% 18% 11% 1	4221
	11th to 20th	Day	45% 9% 15% 24% 7%	4091
	21st to end	Day	41% 7% 12% 31% 8% 1	4312
September	1st to 10th	Day	41% 6% 13% 26% 13% 1	2400
	11th to 20th	Day	38% 7% 11% 25% 18% 1	2400
	21st to end	Day	48% 5% 13% 21% 12% 2	2124
October	1st to 10th	Day	41% 7% 12% 24% 16% 1	3260
	11th to 20th	Day	44% 5% 11% 23% 16% 1	3220
	21st to end	Day	39% 5% 16% 27% 12% 1	3351
November	1st to 10th	Day	46% 6% 13% 21% 12% 2	1761
	11th to 20th	Day	53% 6% 10% 20% 8% 2	1698
	21st to end	Day	58% 6% 14% 17% 6%	1600
December	1st to 10th	Day	65% 8% 10% 14% 3	2600
	11th to 20th	Day	62% 5% 11% 15% 7%	2986
	21st to end	Day	68% 6% 12% 11% 4	3960
January	1st to 10th	Night	64% 5% 11% 13% 7%	6349
	11th to 20th	Night	60% 6% 14% 13% 6% 1	6250
	21st to end	Night	65% 5% 8% 10% 12% 1	6490
February	1st to 10th	Night	58% 6% 13% 16% 7%	2600
	11th to 20th	Night	60% 7% 11% 15% 7% 1	2500
	21st to end	Night	58% 5% 11% 15% 9% 2	1980
March	1st to 10th	Night	58% 4 12% 15% 10% 1	5195
	11th to 20th	Night	49% 6% 17% 19% 6% 4	4980
	21st to end	Night	52% 5% 10% 18% 13% 2	5252
April	1st to 10th	Night	56% 5% 10% 18% 10% 2	2000
	11th to 20th	Night	49% 5% 12% 18% 15% 1	1975
	21st to end	Night	47% 6% 11% 19% 15% 3	2000
May	1st to 10th	Night	60% 6% 8% 17% 7% 1	3796
	11th to 20th	Night	50% 8% 14% 18% 10% 1	3576
	21st to end	Night	49% 9% 12% 18% 12% 1	3927
June	1st to 10th	Night	42% 7% 12% 23% 15% 1	1600
	11th to 20th	Night	42% 8% 14% 24% 12% 1	1600
	21st to end	Night	37% 7% 14% 26% 14% 1	1600
July	1st to 10th	Night	41% 7% 14% 24% 13% 1	3560
	11th to 20th	Night	38% 9% 17% 23% 13%	3552
	21st to end	Night	35% 7% 12% 24% 20% 1	3932
August	1st to 10th	Night	46% 8% 16% 22% 8% 1	2904
	11th to 20th	Night	43% 7% 14% 26% 10%	2991
	21st to end	Night	38% 7% 13% 31% 11% 1	3586
September	1st to 10th	Night	39% 5% 12% 26% 15% 2	2000
	11th to 20th	Night	33% 7% 13% 29% 17% 1	2000
	21st to end	Night	46% 6% 11% 22% 14% 1	2273
October	1st to 10th	Night	46% 7% 11% 22% 13% 1	3920
	11th to 20th	Night	39% 5% 13% 24% 16% 3	3876
	21st to end	Night	40% 5% 15% 27% 12% 1	4195
November	1st to 10th	Night	43% 6% 13% 22% 14% 2	2537
	11th to 20th	Night	51% 6% 13% 19% 10% 2	2700
	21st to end	Night	52% 7% 15% 20% 5%	2800
December	1st to 10th	Night	59% 8% 14% 16% 2	4580
	11th to 20th	Night	58% 5% 12% 14% 10% 1	5208
	21st to end	Night	66% 6% 9% 13% 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	33% 20% 36% 9% 4 1	200
	11th to 20th	Day	37% 29% 26% 7% 1	223
	21st to end	Day	25% 31% 30% 11% 2 1	330
February	1st to 10th	Day	34% 31% 28% 6% 1	300
	11th to 20th	Day	38% 29% 28% 4 1	334
	21st to end	Day	33% 26% 29% 10% 2	414
March	1st to 10th	Day	33% 22% 27% 14% 4	500
	11th to 20th	Day	31% 24% 27% 12% 5% 1	500
	21st to end	Day	31% 26% 26% 12% 4 1	550
April	1st to 10th	Day	32% 23% 26% 15% 3 1	500
	11th to 20th	Day	29% 25% 27% 10% 6% 3	492
	21st to end	Day	28% 21% 29% 15% 6% 2	500
May	1st to 10th	Day	31% 17% 31% 12% 6% 4	503
	11th to 20th	Day	23% 17% 30% 17% 10% 3	527
	21st to end	Day	23% 10% 29% 21% 13% 4	573
June	1st to 10th	Day	17% 17% 32% 21% 12% 2	530
	11th to 20th	Day	18% 13% 27% 27% 13% 1	530
	21st to end	Day	15% 14% 35% 24% 10% 3	530
July	1st to 10th	Day	11% 9% 29% 29% 16% 5%	525
	11th to 20th	Day	7% 8% 29% 30% 21% 4	524
	21st to end	Day	14% 9% 32% 28% 13% 4	576
August	1st to 10th	Day	12% 8% 25% 27% 19% 8%	526
	11th to 20th	Day	16% 8% 25% 29% 14% 8%	519
	21st to end	Day	14% 11% 26% 25% 14% 10%	583
September	1st to 10th	Day	17% 12% 23% 23% 16% 9%	530
	11th to 20th	Day	15% 8% 22% 22% 22% 12%	530
	21st to end	Day	23% 13% 27% 19% 14% 4	530
October	1st to 10th	Day	21% 11% 24% 22% 15% 6%	530
	11th to 20th	Day	24% 18% 28% 21% 7% 2	522
	21st to end	Day	29% 19% 29% 16% 6%	516
November	1st to 10th	Day	23% 20% 26% 19% 11% 1	395
	11th to 20th	Day	28% 21% 27% 18% 5%	298
	21st to end	Day	35% 26% 29% 9% 3	200
December	1st to 10th	Day	32% 24% 30% 10% 4 1	200
	11th to 20th	Day	35% 24% 31% 9% 2	200
	21st to end	Day	35% 20% 31% 12% 1	220
January	1st to 10th	Night	22% 26% 35% 15% 3	800
	11th to 20th	Night	26% 21% 30% 21% 3	800
	21st to end	Night	22% 23% 34% 19% 3	880
February	1st to 10th	Night	25% 21% 32% 21% 1	800
	11th to 20th	Night	28% 23% 33% 15% 1	783
	21st to end	Night	28% 23% 30% 17% 3	660
March	1st to 10th	Night	25% 24% 28% 20% 3	800
	11th to 20th	Night	27% 21% 29% 19% 4	800
	21st to end	Night	25% 21% 30% 19% 5% 1	880
April	1st to 10th	Night	28% 18% 31% 20% 4	800
	11th to 20th	Night	27% 19% 27% 20% 7% 1	791
	21st to end	Night	22% 16% 30% 26% 6%	800
May	1st to 10th	Night	28% 9% 24% 28% 9% 1	492
	11th to 20th	Night	16% 11% 31% 32% 9% 1	394
	21st to end	Night	15% 9% 27% 34% 14%	433
June	1st to 10th	Night	17% 9% 23% 37% 14% 1	400
	11th to 20th	Night	15% 9% 24% 36% 16%	400
	21st to end	Night	12% 4 27% 43% 14% 1	400
July	1st to 10th	Night	9% 4 23% 43% 19% 2	390
	11th to 20th	Night	10% 4 19% 47% 18% 2	388
	21st to end	Night	14% 4 16% 44% 20% 1	488
August	1st to 10th	Night	11% 3 19% 38% 27% 2	597
	11th to 20th	Night	14% 5% 15% 36% 27% 3	644
	21st to end	Night	12% 6% 20% 36% 24% 2	880
September	1st to 10th	Night	15% 7% 25% 33% 19% 2	800
	11th to 20th	Night	12% 7% 19% 29% 30% 5%	800
	21st to end	Night	18% 10% 24% 28% 18% 2	800
October	1st to 10th	Night	21% 9% 24% 26% 19% 2	800
	11th to 20th	Night	23% 12% 27% 28% 8% 1	793
	21st to end	Night	30% 14% 29% 23% 5%	836
November	1st to 10th	Night	18% 17% 29% 27% 8% 1	780
	11th to 20th	Night	26% 17% 31% 19% 7% 1	800
	21st to end	Night	25% 17% 32% 21% 4 1	800
December	1st to 10th	Night	28% 20% 29% 18% 4	800
	11th to 20th	Night	27% 20% 28% 22% 3	800
	21st to end	Night	28% 19% 33% 18% 3	880

Page generated at 2025-10-16 01:50:24. Version ac07

Copyright © 2025 Attilla Danko.