Tecumseh
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Tecumseh clear sky chart from 2005-11-06 to 2026-08-15.

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	11% 7% 3 6% 4 4 4 3 5% 7% 47%	143006
	Night	10% 7% 2 6% 4 4 4 3 5% 7% 49%	139195
Transparency	Day	36% 5% 11% 26% 18% 3	146630
	Night	35% 4 11% 26% 20% 4	143638
Seeing	Day	14% 10% 30% 28% 14% 3	18146
	Night	13% 9% 33% 33% 11% 1	27914

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	13% 10% 3 9% 4 3 3 3 4 6% 42%	5289
	11th to 20th	Day	5% 7% 4 10% 6% 6% 4 3 5% 6% 42%	5310
	21st to end	Day	11% 12% 5% 7% 4 4 3 3 3 5% 43%	5812
February	1st to 10th	Day	12% 11% 4 7% 4 4 3 3 5% 5% 41%	1890
	11th to 20th	Day	10% 10% 3 7% 4 4 4 3 5% 7% 41%	1890
	21st to end	Day	8% 10% 2 6% 3 4 3 3 6% 6% 49%	1754
March	1st to 10th	Day	12% 8% 2 5% 3 3 3 3 3 5% 53%	5046
	11th to 20th	Day	10% 6% 2 5% 2 3 4 3 4 6% 56%	5090
	21st to end	Day	12% 9% 5% 7% 4 5% 5% 4 5% 7% 38%	5583
April	1st to 10th	Day	14% 8% 3 5% 4 3 3 3 4 6% 47%	2378
	11th to 20th	Day	14% 7% 3 6% 4 4 4 4 5% 7% 43%	2511
	21st to end	Day	18% 8% 3 6% 5% 4 5% 3 5% 6% 38%	2730
May	1st to 10th	Day	15% 8% 2 6% 4 3 4 3 4 6% 45%	7617
	11th to 20th	Day	12% 5% 2 5% 4 4 4 3 5% 7% 49%	7627
	21st to end	Day	20% 6% 2 6% 4 4 4 4 6% 7% 37%	8392
June	1st to 10th	Day	6% 4 2 5% 4 4 5% 5% 7% 10% 48%	2798
	11th to 20th	Day	7% 5% 2 5% 4 4 5% 4 6% 9% 48%	2925
	21st to end	Day	7% 4 2 5% 4 5% 5% 4 6% 9% 50%	2730
July	1st to 10th	Day	8% 5% 2 6% 4 4 5% 4 6% 9% 46%	7680
	11th to 20th	Day	6% 4 2 4 4 4 4 4 7% 9% 53%	7680
	21st to end	Day	9% 5% 2 7% 4 5% 5% 5% 7% 9% 42%	8337
August	1st to 10th	Day	6% 4 2 5% 3 4 5% 5% 6% 8% 53%	4364
	11th to 20th	Day	11% 6% 1 6% 4 4 4 3 5% 8% 48%	4224
	21st to end	Day	6% 4 2 4 4 4 4 4 6% 9% 54%	4487
September	1st to 10th	Day	12% 4 1 5% 4 4 3 3 5% 7% 53%	2339
	11th to 20th	Day	9% 5% 2 6% 4 5% 4 4 5% 6% 49%	2200
	21st to end	Day	9% 5% 1 5% 4 3 4 4 5% 6% 55%	2200
October	1st to 10th	Day	10% 5% 2 5% 3 3 2 3 5% 7% 53%	2030
	11th to 20th	Day	11% 5% 1 5% 3 2 3 2 4 5% 57%	2000
	21st to end	Day	17% 6% 1 5% 3 3 3 2 5% 5% 50%	2200
November	1st to 10th	Day	8% 5% 2 5% 3 4 3 3 4 7% 57%	1989
	11th to 20th	Day	11% 5% 2 4 3 4 3 4 3 5% 56%	1890
	21st to end	Day	16% 8% 2 5% 4 3 2 2 5% 6% 48%	1714
December	1st to 10th	Day	6% 5% 2 5% 4 3 4 3 5% 7% 58%	2690
	11th to 20th	Day	9% 7% 3 7% 4 4 4 3 4 6% 50%	3088
	21st to end	Day	18% 14% 7% 11% 4 3 4 3 4 5% 27%	4522
January	1st to 10th	Night	11% 10% 4 13% 5% 4 4 2 4 5% 39%	7634
	11th to 20th	Night	6% 7% 3 7% 4 5% 5% 3 4 6% 50%	7680
	21st to end	Night	13% 10% 4 8% 4 4 4 3 4 6% 41%	8402
February	1st to 10th	Night	10% 12% 3 7% 5% 4 4 3 5% 6% 41%	2730
	11th to 20th	Night	11% 8% 2 8% 5% 4 4 3 5% 6% 45%	2636
	21st to end	Night	10% 7% 2 6% 4 5% 3 3 5% 5% 51%	2050
March	1st to 10th	Night	14% 7% 2 4 3 3 3 2 3 5% 54%	5029
	11th to 20th	Night	8% 5% 2 3 3 3 3 3 5% 8% 57%	5090
	21st to end	Night	14% 7% 3 6% 4 4 4 3 6% 7% 40%	5588
April	1st to 10th	Night	11% 6% 2 6% 4 4 3 2 5% 7% 50%	2242
	11th to 20th	Night	12% 7% 2 6% 4 4 4 4 5% 7% 46%	2055
	21st to end	Night	17% 7% 2 5% 3 5% 4 4 5% 6% 42%	1890
May	1st to 10th	Night	14% 6% 3 5% 4 3 4 3 5% 6% 47%	5266
	11th to 20th	Night	13% 5% 2 5% 3 3 3 3 5% 8% 51%	5265
	21st to end	Night	18% 5% 2 5% 4 3 3 3 5% 6% 45%	5793
June	1st to 10th	Night	6% 4 2 4 3 4 4 4 6% 9% 54%	1806
	11th to 20th	Night	6% 4 2 4 3 4 5% 3 7% 9% 53%	1681
	21st to end	Night	5% 4 1 4 3 3 3 3 6% 8% 59%	1888
July	1st to 10th	Night	6% 4 2 5% 4 4 4 3 6% 8% 53%	5308
	11th to 20th	Night	4 3 2 5% 3 3 4 4 6% 8% 58%	5307
	21st to end	Night	8% 5% 2 6% 4 5% 4 4 7% 10% 45%	5770
August	1st to 10th	Night	2 1 1 4 4 4 5% 4 6% 10% 58%	3016
	11th to 20th	Night	9% 6% 2 5% 4 3 4 3 5% 7% 51%	2924
	21st to end	Night	5% 4 2 5% 3 3 3 3 5% 8% 59%	3416
September	1st to 10th	Night	11% 4 2 5% 3 3 3 3 5% 6% 56%	2057
	11th to 20th	Night	8% 4 1 5% 4 4 4 4 5% 7% 54%	2200
	21st to end	Night	6% 4 2 5% 3 4 4 3 5% 6% 59%	2200
October	1st to 10th	Night	11% 4 2 5% 3 4 3 3 4 6% 55%	2349
	11th to 20th	Night	12% 4 1 4 3 3 3 2 3 6% 58%	2400
	21st to end	Night	15% 7% 2 5% 3 2 3 2 3 4 53%	2640
November	1st to 10th	Night	9% 4 1 4 3 2 3 3 4 5% 61%	2527
	11th to 20th	Night	10% 4 2 4 3 4 3 3 5% 6% 57%	2730
	21st to end	Night	14% 7% 1 4 3 3 3 2 4 5% 53%	2901
December	1st to 10th	Night	6% 6% 3 5% 3 3 3 3 5% 6% 57%	4720
	11th to 20th	Night	11% 7% 3 6% 4 4 4 4 5% 6% 48%	5339
	21st to end	Night	18% 14% 4 8% 4 3 4 3 4 4 34%	6666

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	44% 4 10% 29% 12% 1	5290
	11th to 20th	Day	43% 3 13% 21% 16% 4	5310
	21st to end	Day	46% 3 13% 22% 16% 1	5812
February	1st to 10th	Day	45% 5% 13% 23% 11% 3	1890
	11th to 20th	Day	43% 4 12% 24% 14% 3	1899
	21st to end	Day	36% 3 11% 26% 20% 4	1754
March	1st to 10th	Day	35% 3 9% 20% 23% 10%	5046
	11th to 20th	Day	30% 4 9% 21% 28% 8%	5090
	21st to end	Day	45% 5% 14% 28% 7% 1	5585
April	1st to 10th	Day	39% 4 12% 22% 20% 3	2378
	11th to 20th	Day	41% 5% 12% 22% 18% 2	2511
	21st to end	Day	47% 5% 11% 25% 10% 1	2730
May	1st to 10th	Day	41% 5% 8% 26% 19% 1	7655
	11th to 20th	Day	33% 6% 11% 23% 24% 3	7631
	21st to end	Day	45% 6% 9% 25% 14% 1	8405
June	1st to 10th	Day	28% 8% 17% 28% 17% 2	2798
	11th to 20th	Day	31% 7% 13% 28% 18% 2	2925
	21st to end	Day	30% 7% 14% 29% 17% 4	2730
July	1st to 10th	Day	34% 5% 12% 28% 19% 2	7616
	11th to 20th	Day	26% 6% 14% 28% 20% 7%	7611
	21st to end	Day	36% 6% 13% 32% 11% 2	8155
August	1st to 10th	Day	28% 7% 12% 26% 23% 3	4350
	11th to 20th	Day	35% 5% 15% 27% 16% 1	4263
	21st to end	Day	27% 6% 16% 29% 16% 6%	4486
September	1st to 10th	Day	31% 5% 12% 26% 20% 7%	2339
	11th to 20th	Day	34% 6% 10% 27% 20% 3	2200
	21st to end	Day	29% 6% 9% 28% 25% 3	2200
October	1st to 10th	Day	20% 3 8% 21% 42% 7%	3303
	11th to 20th	Day	19% 3 5% 28% 34% 10%	3240
	21st to end	Day	31% 3 10% 28% 24% 4	3538
November	1st to 10th	Day	29% 5% 12% 30% 19% 5%	1989
	11th to 20th	Day	32% 3 9% 29% 22% 4	1890
	21st to end	Day	38% 4 10% 26% 21% 1	1714
December	1st to 10th	Day	27% 3 12% 39% 17% 1	2690
	11th to 20th	Day	37% 4 12% 33% 13% 1	3085
	21st to end	Day	61% 3 10% 19% 7% 1	4522
January	1st to 10th	Night	49% 4 11% 23% 11% 1	7635
	11th to 20th	Night	36% 3 10% 27% 21% 3	7680
	21st to end	Night	45% 3 12% 18% 16% 4	8402
February	1st to 10th	Night	44% 4 12% 22% 15% 3	2730
	11th to 20th	Night	41% 3 12% 25% 15% 3	2637
	21st to end	Night	36% 4 9% 22% 22% 7%	2050
March	1st to 10th	Night	35% 3 6% 25% 26% 5%	5029
	11th to 20th	Night	25% 4 7% 21% 33% 9%	5090
	21st to end	Night	42% 6% 14% 27% 9% 2	5588
April	1st to 10th	Night	36% 3 11% 23% 23% 4	2242
	11th to 20th	Night	37% 5% 9% 25% 19% 4	2055
	21st to end	Night	42% 6% 11% 25% 14% 2	1890
May	1st to 10th	Night	37% 6% 9% 26% 18% 3	5293
	11th to 20th	Night	33% 5% 11% 25% 22% 6%	5266
	21st to end	Night	40% 6% 11% 26% 17% 1	5805
June	1st to 10th	Night	26% 6% 18% 31% 16% 3	1806
	11th to 20th	Night	26% 8% 13% 31% 18% 4	1681
	21st to end	Night	22% 5% 15% 34% 20% 4	1888
July	1st to 10th	Night	29% 5% 14% 26% 23% 3	5265
	11th to 20th	Night	23% 6% 14% 29% 21% 7%	5256
	21st to end	Night	33% 5% 14% 35% 12% 1	5641
August	1st to 10th	Night	20% 6% 18% 28% 22% 6%	3006
	11th to 20th	Night	32% 5% 13% 28% 19% 2	2951
	21st to end	Night	24% 5% 13% 35% 18% 5%	3416
September	1st to 10th	Night	30% 4 10% 27% 20% 8%	2057
	11th to 20th	Night	27% 6% 11% 28% 23% 5%	2200
	21st to end	Night	27% 4 8% 25% 31% 4	2200
October	1st to 10th	Night	21% 3 6% 17% 47% 7%	3843
	11th to 20th	Night	21% 2 5% 29% 29% 13%	3899
	21st to end	Night	32% 2 8% 29% 27% 3	4252
November	1st to 10th	Night	27% 3 12% 29% 23% 6%	2527
	11th to 20th	Night	29% 3 11% 29% 23% 5%	2730
	21st to end	Night	35% 3 10% 30% 19% 3	2901
December	1st to 10th	Night	28% 4 14% 34% 19% 1	4720
	11th to 20th	Night	37% 3 12% 29% 16% 2	5341
	21st to end	Night	55% 4 9% 23% 8% 1	6666

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% 16% 36% 22% 6%	330
	11th to 20th	Day	21% 20% 40% 17% 3	330
	21st to end	Day	12% 13% 48% 22% 3	363
February	1st to 10th	Day	19% 21% 39% 18% 2	330
	11th to 20th	Day	19% 19% 43% 13% 6%	330
	21st to end	Day	11% 27% 42% 15% 4	273
March	1st to 10th	Day	17% 17% 42% 22% 2	330
	11th to 20th	Day	25% 15% 35% 19% 5% 1	330
	21st to end	Day	26% 22% 39% 10% 3 1	363
April	1st to 10th	Day	24% 19% 35% 18% 5%	398
	11th to 20th	Day	19% 16% 39% 21% 4 1	549
	21st to end	Day	23% 15% 36% 18% 8%	750
May	1st to 10th	Day	17% 15% 35% 23% 8% 1	753
	11th to 20th	Day	17% 10% 31% 28% 11% 2	775
	21st to end	Day	18% 9% 30% 26% 13% 2	844
June	1st to 10th	Day	6% 5% 25% 34% 24% 6%	780
	11th to 20th	Day	8% 5% 31% 35% 17% 4	780
	21st to end	Day	8% 6% 35% 36% 13% 2	780
July	1st to 10th	Day	8% 3 19% 33% 28% 8%	771
	11th to 20th	Day	4 3 18% 39% 28% 9%	768
	21st to end	Day	8% 3 19% 35% 27% 8%	849
August	1st to 10th	Day	7% 3 20% 40% 25% 5%	776
	11th to 20th	Day	9% 2 19% 41% 24% 5%	736
	21st to end	Day	11% 1 15% 36% 30% 7%	693
September	1st to 10th	Day	13% 3 18% 36% 26% 4	469
	11th to 20th	Day	6% 3 23% 38% 25% 4	330
	21st to end	Day	14% 5% 28% 33% 15% 5%	330
October	1st to 10th	Day	12% 8% 31% 30% 15% 5%	330
	11th to 20th	Day	9% 18% 42% 20% 10% 1	330
	21st to end	Day	24% 16% 34% 18% 7% 1	363
November	1st to 10th	Day	14% 16% 38% 24% 7% 2	330
	11th to 20th	Day	13% 18% 36% 24% 8%	330
	21st to end	Day	23% 15% 35% 19% 8%	330
December	1st to 10th	Day	9% 16% 40% 27% 5% 2	330
	11th to 20th	Day	16% 16% 40% 21% 6% 1	330
	21st to end	Day	21% 19% 36% 21% 2	363
January	1st to 10th	Night	12% 13% 38% 30% 6%	1050
	11th to 20th	Night	15% 13% 39% 27% 5%	1050
	21st to end	Night	14% 12% 41% 29% 4	1155
February	1st to 10th	Night	17% 13% 40% 26% 3	1050
	11th to 20th	Night	15% 15% 39% 27% 3	1002
	21st to end	Night	14% 14% 42% 25% 6%	666
March	1st to 10th	Night	15% 13% 42% 25% 5%	630
	11th to 20th	Night	18% 11% 38% 27% 4 1	630
	21st to end	Night	22% 14% 38% 22% 4	693
April	1st to 10th	Night	14% 13% 42% 25% 6%	630
	11th to 20th	Night	16% 16% 40% 24% 4	623
	21st to end	Night	20% 11% 38% 24% 6% 1	630
May	1st to 10th	Night	17% 9% 36% 31% 6% 1	630
	11th to 20th	Night	14% 10% 32% 33% 11%	621
	21st to end	Night	13% 6% 32% 34% 13% 2	683
June	1st to 10th	Night	7% 4 24% 42% 22% 1	630
	11th to 20th	Night	8% 4 30% 42% 16% 1	630
	21st to end	Night	5% 6% 33% 43% 12% 1	630
July	1st to 10th	Night	7% 3 17% 45% 27% 1	615
	11th to 20th	Night	3 1 18% 48% 27% 2	612
	21st to end	Night	7% 2 17% 47% 26% 1	690
August	1st to 10th	Night	4 2 18% 48% 26% 2	627
	11th to 20th	Night	6% 1 14% 50% 26% 2	606
	21st to end	Night	7% 2 17% 43% 30% 2	660
September	1st to 10th	Night	12% 4 19% 43% 21% 2	600
	11th to 20th	Night	9% 1 23% 44% 21% 2	600
	21st to end	Night	7% 3 26% 43% 19% 1	600
October	1st to 10th	Night	13% 5% 30% 33% 19% 1	749
	11th to 20th	Night	14% 8% 41% 30% 7%	800
	21st to end	Night	19% 12% 35% 26% 8%	880
November	1st to 10th	Night	11% 10% 34% 33% 11% 1	887
	11th to 20th	Night	12% 14% 37% 30% 7%	1050
	21st to end	Night	18% 11% 34% 30% 6%	1050
December	1st to 10th	Night	13% 12% 38% 31% 5% 1	1050
	11th to 20th	Night	16% 11% 41% 27% 5%	1050
	21st to end	Night	18% 14% 35% 28% 4	1155

Page generated at 2026-08-12 02:37:18. Version ac07

Copyright © 2026 Attilla Danko.