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 2025-04-11.

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%	113477
	Night	10% 7% 2 6% 4 4 4 3 5% 6% 49%	114978
Transparency	Day	36% 5% 12% 26% 18% 3	117142
	Night	34% 4 11% 26% 20% 4	119442
Seeing	Day	14% 10% 30% 28% 15% 3	16148
	Night	13% 9% 33% 33% 11% 1	26192

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	15% 9% 3 9% 5% 4 3 3 5% 7% 38%	4077
	11th to 20th	Day	7% 9% 4 10% 6% 7% 5% 3 4 6% 40%	4080
	21st to end	Day	11% 12% 5% 7% 4 4 3 3 4 5% 41%	4488
February	1st to 10th	Day	12% 12% 4 7% 4 5% 3 3 5% 5% 40%	1800
	11th to 20th	Day	10% 11% 3 7% 4 4 4 4 5% 6% 41%	1798
	21st to end	Day	9% 10% 3 6% 3 4 3 3 6% 6% 48%	1673
March	1st to 10th	Day	12% 8% 2 5% 3 3 3 3 3 5% 54%	4936
	11th to 20th	Day	11% 6% 2 5% 2 3 4 3 5% 6% 55%	4980
	21st to end	Day	12% 9% 5% 7% 4 5% 5% 4 5% 7% 37%	5462
April	1st to 10th	Day	14% 7% 3 5% 4 3 4 3 4 6% 47%	2265
	11th to 20th	Day	14% 8% 3 7% 4 4 4 4 5% 7% 42%	2269
	21st to end	Day	18% 7% 3 6% 5% 4 5% 3 5% 6% 39%	2470
May	1st to 10th	Day	15% 9% 3 7% 4 3 4 3 4 6% 40%	4082
	11th to 20th	Day	15% 7% 3 6% 4 5% 4 4 5% 8% 40%	4082
	21st to end	Day	13% 6% 2 6% 4 4 4 4 6% 8% 44%	4477
June	1st to 10th	Day	5% 4 2 4 4 5% 5% 5% 7% 11% 49%	2532
	11th to 20th	Day	7% 4 2 5% 4 4 5% 4 6% 10% 48%	2647
	21st to end	Day	6% 4 2 4 4 4 5% 4 6% 8% 52%	2470
July	1st to 10th	Day	11% 6% 2 6% 4 4 5% 4 6% 8% 43%	4120
	11th to 20th	Day	5% 3 2 4 4 4 4 4 8% 10% 53%	4120
	21st to end	Day	5% 4 2 5% 4 4 5% 5% 8% 9% 49%	4465
August	1st to 10th	Day	6% 4 2 4 3 4 5% 5% 6% 8% 53%	4104
	11th to 20th	Day	11% 6% 2 6% 4 4 4 3 5% 8% 47%	4041
	21st to end	Day	5% 4 2 4 4 4 4 4 6% 9% 55%	4350
September	1st to 10th	Day	11% 4 1 5% 4 4 3 2 5% 7% 54%	2222
	11th to 20th	Day	9% 5% 2 6% 4 5% 4 4 5% 6% 50%	2090
	21st to end	Day	9% 5% 1 5% 3 3 4 4 5% 6% 55%	2090
October	1st to 10th	Day	10% 5% 2 5% 3 3 2 3 5% 8% 53%	1929
	11th to 20th	Day	11% 6% 1 5% 3 2 3 2 3 5% 58%	1900
	21st to end	Day	15% 6% 1 5% 3 3 4 3 5% 5% 50%	2090
November	1st to 10th	Day	9% 6% 2 5% 3 4 3 3 4 7% 55%	1893
	11th to 20th	Day	12% 6% 2 4 3 4 3 4 3 5% 56%	1800
	21st to end	Day	15% 7% 2 5% 4 3 2 2 5% 6% 50%	1633
December	1st to 10th	Day	6% 5% 1 4 4 3 4 3 5% 6% 58%	2610
	11th to 20th	Day	9% 7% 3 7% 4 4 3 3 4 6% 50%	3008
	21st to end	Day	19% 15% 7% 11% 4 3 4 3 4 5% 26%	4424
January	1st to 10th	Night	11% 10% 4 14% 5% 4 4 3 4 5% 36%	5888
	11th to 20th	Night	8% 7% 4 8% 4 6% 5% 3 4 6% 45%	5900
	21st to end	Night	14% 9% 4 8% 4 4 3 3 4 5% 42%	6490
February	1st to 10th	Night	11% 12% 3 7% 5% 4 4 3 5% 6% 40%	2600
	11th to 20th	Night	11% 8% 2 8% 5% 4 4 3 5% 5% 45%	2508
	21st to end	Night	10% 7% 2 6% 4 5% 3 3 5% 5% 50%	1955
March	1st to 10th	Night	14% 7% 2 4 3 3 3 2 3 5% 55%	4919
	11th to 20th	Night	8% 5% 2 3 3 3 3 3 6% 8% 57%	4980
	21st to end	Night	14% 8% 3 6% 4 4 4 3 6% 7% 40%	5467
April	1st to 10th	Night	11% 6% 2 6% 4 4 3 2 5% 7% 51%	2135
	11th to 20th	Night	12% 8% 2 6% 4 4 4 3 5% 7% 46%	1863
	21st to end	Night	17% 7% 2 5% 3 5% 5% 4 5% 5% 43%	1710
May	1st to 10th	Night	15% 8% 3 5% 4 4 4 3 6% 7% 42%	2823
	11th to 20th	Night	14% 6% 2 6% 4 4 4 3 5% 8% 44%	2823
	21st to end	Night	11% 4 2 4 3 3 3 3 5% 7% 54%	3090
June	1st to 10th	Night	5% 4 2 4 3 4 4 4 6% 9% 56%	1634
	11th to 20th	Night	6% 4 2 4 3 4 5% 4 7% 9% 53%	1521
	21st to end	Night	4 3 1 4 3 3 3 4 6% 8% 60%	1708
July	1st to 10th	Night	9% 6% 2 6% 4 3 4 3 5% 6% 51%	2850
	11th to 20th	Night	2 2 1 4 3 3 3 4 7% 10% 60%	2850
	21st to end	Night	5% 3 2 5% 4 4 4 4 7% 10% 51%	3098
August	1st to 10th	Night	2 1 1 4 4 4 5% 5% 6% 11% 57%	2836
	11th to 20th	Night	9% 6% 2 5% 4 4 4 3 5% 7% 51%	2798
	21st to end	Night	5% 3 2 5% 3 3 3 3 5% 8% 59%	3311
September	1st to 10th	Night	10% 4 2 5% 3 3 3 3 5% 5% 56%	1954
	11th to 20th	Night	8% 4 1 4 4 3 4 4 5% 7% 55%	2090
	21st to end	Night	6% 4 2 5% 3 4 4 3 4 6% 59%	2090
October	1st to 10th	Night	11% 4 1 5% 3 4 3 3 4 6% 55%	2231
	11th to 20th	Night	12% 4 1 4 3 3 2 2 3 6% 59%	2280
	21st to end	Night	14% 7% 2 5% 3 2 3 2 3 4 54%	2508
November	1st to 10th	Night	9% 4 1 4 3 2 3 3 4 5% 61%	2404
	11th to 20th	Night	10% 5% 2 4 4 4 3 3 5% 5% 56%	2600
	21st to end	Night	13% 7% 1 3 3 3 3 2 4 5% 54%	2763
December	1st to 10th	Night	6% 6% 3 4 3 3 3 3 5% 6% 58%	4580
	11th to 20th	Night	11% 7% 3 6% 4 4 4 4 5% 6% 47%	5199
	21st to end	Night	19% 14% 4 8% 4 3 4 2 4 4 33%	6522

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	47% 5% 11% 26% 11% 1	4078
	11th to 20th	Day	46% 3 12% 20% 16% 4	4080
	21st to end	Day	46% 3 13% 19% 17% 2	4488
February	1st to 10th	Day	47% 5% 13% 23% 10% 3	1800
	11th to 20th	Day	43% 4 12% 24% 14% 3	1807
	21st to end	Day	37% 3 11% 26% 18% 4	1673
March	1st to 10th	Day	34% 3 9% 21% 23% 10%	4936
	11th to 20th	Day	30% 4 8% 21% 28% 8%	4980
	21st to end	Day	45% 5% 15% 28% 6% 1	5464
April	1st to 10th	Day	38% 4 12% 23% 20% 3	2265
	11th to 20th	Day	42% 5% 12% 23% 17% 1	2269
	21st to end	Day	46% 5% 11% 26% 11% 1	2470
May	1st to 10th	Day	45% 6% 9% 23% 15% 2	4120
	11th to 20th	Day	40% 8% 14% 21% 17%	4086
	21st to end	Day	37% 7% 10% 30% 14% 2	4489
June	1st to 10th	Day	26% 8% 17% 29% 17% 2	2532
	11th to 20th	Day	31% 7% 13% 29% 17% 2	2647
	21st to end	Day	28% 7% 14% 29% 18% 4	2470
July	1st to 10th	Day	38% 6% 13% 23% 18% 3	4056
	11th to 20th	Day	25% 7% 13% 34% 19% 3	4051
	21st to end	Day	27% 7% 16% 30% 17% 3	4325
August	1st to 10th	Day	28% 7% 12% 26% 23% 3	4090
	11th to 20th	Day	36% 5% 15% 26% 16% 1	4080
	21st to end	Day	26% 6% 17% 29% 17% 6%	4349
September	1st to 10th	Day	30% 5% 12% 26% 20% 7%	2222
	11th to 20th	Day	33% 6% 9% 27% 21% 3	2090
	21st to end	Day	29% 6% 9% 28% 25% 3	2090
October	1st to 10th	Day	19% 3 8% 21% 41% 8%	3202
	11th to 20th	Day	19% 2 5% 29% 35% 11%	3140
	21st to end	Day	30% 4 10% 28% 25% 4	3428
November	1st to 10th	Day	30% 5% 12% 29% 19% 6%	1893
	11th to 20th	Day	32% 3 10% 28% 23% 4	1800
	21st to end	Day	37% 4 10% 26% 22% 1	1633
December	1st to 10th	Day	27% 3 12% 40% 17% 1	2610
	11th to 20th	Day	37% 4 12% 33% 13% 1	3005
	21st to end	Day	61% 3 9% 18% 7% 1	4424
January	1st to 10th	Night	51% 4 11% 23% 11% 1	5888
	11th to 20th	Night	41% 3 11% 23% 19% 3	5900
	21st to end	Night	44% 3 12% 18% 18% 5%	6490
February	1st to 10th	Night	45% 4 12% 22% 14% 3	2600
	11th to 20th	Night	42% 3 11% 24% 16% 3	2509
	21st to end	Night	36% 4 9% 23% 21% 7%	1955
March	1st to 10th	Night	35% 3 6% 26% 26% 5%	4919
	11th to 20th	Night	25% 4 7% 21% 34% 9%	4980
	21st to end	Night	42% 6% 14% 27% 8% 2	5467
April	1st to 10th	Night	35% 3 11% 24% 23% 4	2135
	11th to 20th	Night	37% 6% 9% 26% 19% 3	1863
	21st to end	Night	41% 6% 11% 25% 15% 2	1710
May	1st to 10th	Night	40% 8% 14% 21% 15% 3	2850
	11th to 20th	Night	38% 7% 13% 26% 17% 1	2824
	21st to end	Night	29% 7% 14% 31% 18% 1	3099
June	1st to 10th	Night	24% 7% 17% 33% 16% 3	1634
	11th to 20th	Night	25% 8% 13% 32% 18% 3	1521
	21st to end	Night	20% 5% 15% 34% 21% 4	1708
July	1st to 10th	Night	34% 6% 12% 23% 20% 5%	2805
	11th to 20th	Night	17% 6% 14% 35% 25% 3	2796
	21st to end	Night	26% 6% 18% 31% 18% 1	2999
August	1st to 10th	Night	20% 6% 18% 27% 22% 6%	2826
	11th to 20th	Night	33% 5% 14% 27% 20% 2	2825
	21st to end	Night	24% 5% 13% 35% 18% 5%	3311
September	1st to 10th	Night	29% 5% 10% 27% 21% 9%	1954
	11th to 20th	Night	27% 6% 11% 27% 25% 5%	2090
	21st to end	Night	27% 4 8% 26% 31% 4	2090
October	1st to 10th	Night	20% 3 6% 17% 47% 7%	3725
	11th to 20th	Night	20% 2 5% 29% 30% 14%	3779
	21st to end	Night	31% 2 8% 29% 27% 3	4120
November	1st to 10th	Night	27% 3 12% 28% 23% 7%	2404
	11th to 20th	Night	30% 3 11% 28% 24% 5%	2600
	21st to end	Night	34% 3 10% 30% 20% 3	2763
December	1st to 10th	Night	28% 4 14% 34% 20% 1	4580
	11th to 20th	Night	37% 3 12% 29% 16% 2	5201
	21st to end	Night	55% 4 9% 23% 7% 1	6522

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	21% 16% 35% 22% 6%	300
	11th to 20th	Day	23% 18% 40% 17% 3	300
	21st to end	Day	12% 13% 49% 22% 3	330
February	1st to 10th	Day	21% 21% 39% 17% 2	300
	11th to 20th	Day	19% 21% 43% 12% 5%	300
	21st to end	Day	11% 28% 43% 14% 4	249
March	1st to 10th	Day	15% 18% 43% 22% 2	300
	11th to 20th	Day	24% 15% 37% 18% 5%	300
	21st to end	Day	27% 21% 39% 10% 3	330
April	1st to 10th	Day	23% 19% 34% 18% 6%	365
	11th to 20th	Day	18% 15% 38% 23% 5% 1	467
	21st to end	Day	22% 15% 36% 18% 9%	650
May	1st to 10th	Day	18% 17% 36% 21% 8%	653
	11th to 20th	Day	18% 8% 32% 29% 12% 2	675
	21st to end	Day	17% 10% 31% 26% 14% 2	734
June	1st to 10th	Day	5% 5% 23% 36% 26% 5%	680
	11th to 20th	Day	6% 5% 30% 36% 18% 5%	680
	21st to end	Day	7% 7% 34% 38% 13% 2	680
July	1st to 10th	Day	10% 3 18% 33% 28% 9%	671
	11th to 20th	Day	4 2 19% 40% 28% 6%	668
	21st to end	Day	8% 3 19% 35% 28% 8%	739
August	1st to 10th	Day	8% 3 17% 41% 27% 5%	676
	11th to 20th	Day	9% 2 21% 41% 23% 4	665
	21st to end	Day	10% 1 15% 36% 31% 7%	644
September	1st to 10th	Day	13% 2 19% 36% 26% 4	432
	11th to 20th	Day	6% 3 24% 38% 25% 4	300
	21st to end	Day	14% 6% 29% 34% 13% 4	300
October	1st to 10th	Day	12% 8% 29% 29% 15% 6%	300
	11th to 20th	Day	9% 18% 42% 20% 10% 1	300
	21st to end	Day	21% 17% 35% 19% 8% 1	330
November	1st to 10th	Day	15% 15% 36% 25% 8% 2	300
	11th to 20th	Day	15% 19% 35% 23% 7%	300
	21st to end	Day	22% 14% 36% 19% 8%	300
December	1st to 10th	Day	8% 17% 40% 27% 6% 2	300
	11th to 20th	Day	16% 17% 39% 21% 6% 1	300
	21st to end	Day	22% 21% 36% 18% 2	330
January	1st to 10th	Night	13% 13% 38% 30% 7%	1000
	11th to 20th	Night	15% 13% 38% 28% 5% 1	1000
	21st to end	Night	14% 12% 41% 29% 4	1100
February	1st to 10th	Night	18% 14% 40% 26% 3	1000
	11th to 20th	Night	15% 15% 40% 27% 3	954
	21st to end	Night	14% 14% 42% 25% 6%	635
March	1st to 10th	Night	14% 13% 43% 26% 5%	600
	11th to 20th	Night	18% 11% 38% 28% 5% 1	600
	21st to end	Night	23% 14% 38% 22% 4	660
April	1st to 10th	Night	14% 13% 42% 25% 6%	600
	11th to 20th	Night	16% 13% 42% 25% 5%	565
	21st to end	Night	20% 11% 37% 25% 6% 1	570
May	1st to 10th	Night	17% 9% 37% 30% 6% 1	570
	11th to 20th	Night	14% 9% 32% 34% 11% 1	561
	21st to end	Night	12% 6% 33% 34% 14% 2	617
June	1st to 10th	Night	6% 4 24% 42% 23% 1	570
	11th to 20th	Night	7% 3 29% 43% 16% 1	570
	21st to end	Night	4 5% 34% 45% 12% 1	570
July	1st to 10th	Night	8% 3 15% 46% 27% 2	555
	11th to 20th	Night	3 1 18% 50% 26% 2	552
	21st to end	Night	7% 2 16% 47% 26% 2	624
August	1st to 10th	Night	4 1 17% 48% 28% 2	567
	11th to 20th	Night	7% 1 15% 50% 26% 2	564
	21st to end	Night	7% 1 17% 42% 31% 2	627
September	1st to 10th	Night	12% 3 19% 43% 21% 2	570
	11th to 20th	Night	9% 1 23% 43% 21% 2	570
	21st to end	Night	8% 4 27% 43% 18% 1	570
October	1st to 10th	Night	13% 5% 29% 34% 19% 1	711
	11th to 20th	Night	14% 8% 41% 30% 7%	760
	21st to end	Night	18% 12% 35% 27% 8%	836
November	1st to 10th	Night	11% 10% 33% 34% 11% 1	844
	11th to 20th	Night	12% 14% 38% 29% 7%	1000
	21st to end	Night	17% 11% 36% 30% 7%	1000
December	1st to 10th	Night	13% 12% 38% 31% 6% 1	1000
	11th to 20th	Night	17% 11% 40% 27% 5%	1000
	21st to end	Night	19% 14% 35% 27% 4	1100

Page generated at 2025-04-08 08:17:25. Version ac07

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