Kalamazoo
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Kalamazoo clear sky chart from 2005-11-06 to 2024-03-28.

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	14% 11% 5% 8% 6% 4 5% 5% 5% 7% 32%	78702
	Night	16% 12% 5% 8% 6% 3 4 4 5% 6% 30%	81346
Transparency	Day	51% 7% 12% 19% 11% 1	78405
	Night	54% 6% 11% 17% 10% 1	81164
Seeing	Day	18% 15% 30% 22% 12% 4	14835
	Night	20% 12% 30% 27% 11% 1	24885

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% 20% 8% 11% 8% 4 4 5% 4 5% 15%	2527
	11th to 20th	Day	13% 20% 8% 12% 11% 10% 7% 3 3 4 9%	2530
	21st to end	Day	23% 22% 9% 13% 7% 3 3 3 3 4 9%	2787
February	1st to 10th	Day	14% 13% 8% 13% 12% 6% 5% 3 4 5% 17%	1786
	11th to 20th	Day	15% 12% 7% 15% 10% 4 5% 3 4 4 21%	1848
	21st to end	Day	16% 15% 8% 13% 7% 4 5% 4 4 5% 22%	1570
March	1st to 10th	Day	13% 12% 5% 9% 7% 5% 5% 5% 6% 7% 27%	1900
	11th to 20th	Day	12% 10% 4 10% 6% 4 4 4 5% 7% 33%	2035
	21st to end	Day	19% 12% 5% 8% 7% 4 4 4 5% 6% 27%	2325
April	1st to 10th	Day	18% 13% 5% 6% 7% 3 4 4 5% 6% 29%	2160
	11th to 20th	Day	17% 11% 3 6% 4 3 4 5% 4 7% 35%	2177
	21st to end	Day	18% 10% 4 6% 6% 3 5% 4 5% 7% 34%	2340
May	1st to 10th	Day	17% 8% 3 6% 6% 3 6% 5% 6% 7% 32%	2340
	11th to 20th	Day	18% 7% 3 6% 6% 3 4 5% 5% 7% 37%	2301
	21st to end	Day	12% 6% 3 5% 6% 3 5% 5% 6% 9% 41%	2684
June	1st to 10th	Day	10% 5% 3 6% 6% 3 4 5% 6% 9% 43%	2520
	11th to 20th	Day	10% 5% 3 6% 4 4 4 5% 6% 9% 44%	2520
	21st to end	Day	10% 6% 3 5% 5% 3 6% 5% 7% 9% 39%	2520
July	1st to 10th	Day	6% 5% 2 5% 5% 3 5% 4 7% 11% 48%	2520
	11th to 20th	Day	10% 5% 2 4 5% 3 5% 5% 6% 9% 46%	2520
	21st to end	Day	8% 3 2 6% 5% 3 6% 7% 7% 10% 45%	2739
August	1st to 10th	Day	9% 5% 2 5% 6% 3 5% 6% 7% 11% 42%	2327
	11th to 20th	Day	10% 4 2 5% 6% 4 6% 5% 6% 8% 43%	2303
	21st to end	Day	11% 5% 3 5% 6% 3 5% 5% 5% 9% 45%	2396
September	1st to 10th	Day	12% 6% 3 6% 6% 4 5% 5% 5% 7% 43%	2124
	11th to 20th	Day	12% 5% 2 5% 4 3 4 5% 6% 8% 46%	1980
	21st to end	Day	12% 7% 4 7% 5% 4 4 4 6% 8% 40%	1980
October	1st to 10th	Day	15% 7% 3 6% 5% 3 5% 4 4 6% 41%	1980
	11th to 20th	Day	20% 10% 4 7% 7% 3 5% 6% 5% 7% 27%	1773
	21st to end	Day	23% 12% 3 9% 6% 3 5% 4 4 5% 25%	1782
November	1st to 10th	Day	13% 12% 4 5% 5% 3 4 5% 5% 7% 37%	1672
	11th to 20th	Day	16% 17% 6% 10% 6% 3 5% 4 5% 5% 23%	1710
	21st to end	Day	20% 16% 7% 9% 6% 3 4 3 5% 6% 21%	1710
December	1st to 10th	Day	15% 20% 12% 10% 6% 3 5% 4 4 4 17%	1615
	11th to 20th	Day	13% 20% 10% 13% 7% 4 4 4 5% 4 16%	1918
	21st to end	Day	21% 25% 8% 11% 8% 3 3 3 3 6% 9%	2783
January	1st to 10th	Night	17% 18% 10% 14% 8% 3 5% 4 3 4 15%	4428
	11th to 20th	Night	14% 19% 10% 15% 9% 5% 7% 4 4 4 10%	4440
	21st to end	Night	26% 16% 9% 15% 8% 3 4 3 3 3 10%	4880
February	1st to 10th	Night	14% 17% 7% 11% 10% 5% 4 3 4 5% 20%	2390
	11th to 20th	Night	14% 13% 7% 12% 10% 4 4 4 4 5% 24%	2218
	21st to end	Night	18% 11% 6% 10% 7% 3 4 4 5% 5% 26%	1884
March	1st to 10th	Night	16% 10% 5% 9% 7% 3 4 3 4 6% 33%	2280
	11th to 20th	Night	13% 9% 3 6% 6% 3 4 5% 5% 7% 39%	2144
	21st to end	Night	21% 9% 5% 7% 5% 3 5% 3 4 8% 31%	2201
April	1st to 10th	Night	15% 9% 5% 7% 5% 4 5% 4 5% 8% 35%	1800
	11th to 20th	Night	18% 10% 3 5% 6% 3 4 5% 5% 6% 36%	1731
	21st to end	Night	18% 8% 3 6% 5% 3 3 5% 5% 7% 38%	1620
May	1st to 10th	Night	17% 10% 3 7% 6% 4 4 4 5% 7% 34%	1620
	11th to 20th	Night	19% 7% 2 5% 4 3 4 3 5% 7% 40%	1592
	21st to end	Night	11% 6% 2 6% 6% 3 4 5% 6% 10% 41%	1588
June	1st to 10th	Night	10% 5% 1 5% 4 2 4 4 6% 11% 47%	1440
	11th to 20th	Night	11% 5% 3 5% 4 3 5% 5% 6% 10% 45%	1440
	21st to end	Night	9% 4 2 5% 5% 3 5% 6% 6% 9% 45%	1440
July	1st to 10th	Night	6% 3 2 4 4 4 5% 4 5% 10% 52%	1440
	11th to 20th	Night	8% 4 2 5% 4 2 4 4 6% 9% 53%	1440
	21st to end	Night	6% 4 2 4 5% 3 6% 5% 7% 9% 50%	1579
August	1st to 10th	Night	8% 4 1 4 4 3 5% 6% 6% 10% 50%	1611
	11th to 20th	Night	9% 4 2 5% 5% 3 5% 5% 6% 7% 49%	1598
	21st to end	Night	8% 5% 2 5% 4 3 5% 4 5% 6% 51%	1957
September	1st to 10th	Night	9% 6% 2 5% 5% 2 4 4 6% 8% 48%	1818
	11th to 20th	Night	11% 6% 2 5% 3 3 3 4 4 7% 52%	1980
	21st to end	Night	13% 7% 3 6% 5% 3 5% 4 5% 6% 44%	1980
October	1st to 10th	Night	16% 7% 2 5% 5% 3 4 4 4 6% 44%	1980
	11th to 20th	Night	18% 11% 4 7% 7% 3 4 3 4 6% 34%	2183
	21st to end	Night	25% 10% 2 6% 5% 3 4 4 4 5% 31%	2574
November	1st to 10th	Night	14% 11% 4 6% 6% 3 3 5% 4 5% 39%	2406
	11th to 20th	Night	15% 16% 5% 9% 6% 3 5% 4 5% 7% 25%	2470
	21st to end	Night	19% 15% 6% 8% 6% 3 4 4 5% 6% 25%	2470
December	1st to 10th	Night	17% 20% 9% 11% 6% 3 4 4 5% 5% 16%	2561
	11th to 20th	Night	15% 19% 10% 14% 7% 3 4 4 4 4 17%	3279
	21st to end	Night	26% 21% 7% 9% 6% 3 4 4 4 4 11%	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	69% 8% 11% 10% 2	2528
	11th to 20th	Day	79% 8% 7% 4 1	2530
	21st to end	Day	79% 5% 7% 7% 2	2787
February	1st to 10th	Day	70% 5% 9% 10% 5% 1	1786
	11th to 20th	Day	66% 5% 9% 13% 7%	1858
	21st to end	Day	64% 6% 12% 12% 5% 1	1570
March	1st to 10th	Day	55% 7% 13% 19% 7%	1900
	11th to 20th	Day	51% 6% 11% 19% 11% 2	2035
	21st to end	Day	59% 6% 10% 19% 6% 1	2325
April	1st to 10th	Day	55% 6% 10% 19% 11%	2160
	11th to 20th	Day	48% 6% 11% 20% 13% 2	2177
	21st to end	Day	49% 6% 13% 16% 14% 2	2340
May	1st to 10th	Day	49% 7% 13% 20% 9% 1	2340
	11th to 20th	Day	47% 6% 11% 20% 14% 1	2305
	21st to end	Day	40% 8% 14% 24% 14% 1	2684
June	1st to 10th	Day	36% 8% 12% 26% 16% 2	2520
	11th to 20th	Day	36% 7% 13% 24% 19% 2	2520
	21st to end	Day	38% 10% 14% 20% 15% 2	2520
July	1st to 10th	Day	31% 7% 13% 26% 19% 4	2451
	11th to 20th	Day	33% 8% 13% 27% 16% 3	2445
	21st to end	Day	30% 10% 15% 25% 18% 2	2587
August	1st to 10th	Day	33% 9% 16% 26% 13% 2	2314
	11th to 20th	Day	36% 8% 15% 27% 12% 2	2303
	21st to end	Day	35% 7% 12% 26% 17% 4	2396
September	1st to 10th	Day	40% 7% 14% 22% 15% 3	2124
	11th to 20th	Day	34% 7% 12% 31% 16% 1	1980
	21st to end	Day	40% 7% 12% 24% 16% 1	1980
October	1st to 10th	Day	44% 7% 10% 24% 14% 2	1980
	11th to 20th	Day	54% 6% 11% 20% 8%	1773
	21st to end	Day	61% 5% 11% 15% 7% 1	1782
November	1st to 10th	Day	46% 7% 12% 21% 13% 1	1672
	11th to 20th	Day	62% 6% 10% 15% 6% 1	1710
	21st to end	Day	65% 5% 13% 13% 4	1710
December	1st to 10th	Day	70% 5% 10% 11% 3	1615
	11th to 20th	Day	69% 8% 10% 11% 2	1915
	21st to end	Day	77% 6% 8% 7% 2	2783
January	1st to 10th	Night	71% 7% 9% 9% 4	4428
	11th to 20th	Night	77% 7% 7% 5% 3	4440
	21st to end	Night	79% 6% 8% 5% 2	4880
February	1st to 10th	Night	66% 6% 9% 12% 6% 1	2390
	11th to 20th	Night	62% 5% 10% 16% 7%	2219
	21st to end	Night	60% 5% 13% 14% 6% 2	1884
March	1st to 10th	Night	53% 5% 12% 21% 8% 1	2280
	11th to 20th	Night	44% 7% 13% 21% 14% 2	2144
	21st to end	Night	53% 5% 10% 20% 9% 1	2201
April	1st to 10th	Night	47% 7% 12% 21% 12% 1	1800
	11th to 20th	Night	48% 5% 9% 17% 17% 3	1731
	21st to end	Night	45% 7% 12% 19% 15% 2	1620
May	1st to 10th	Night	50% 6% 12% 20% 10% 2	1620
	11th to 20th	Night	44% 6% 11% 20% 17% 2	1593
	21st to end	Night	38% 9% 14% 24% 14% 2	1589
June	1st to 10th	Night	31% 6% 13% 30% 18% 2	1440
	11th to 20th	Night	33% 9% 14% 24% 19% 2	1440
	21st to end	Night	33% 9% 15% 24% 16% 2	1440
July	1st to 10th	Night	28% 7% 15% 26% 20% 4	1400
	11th to 20th	Night	28% 8% 13% 27% 21% 3	1392
	21st to end	Night	28% 8% 16% 24% 20% 4	1491
August	1st to 10th	Night	27% 9% 15% 30% 18% 2	1600
	11th to 20th	Night	32% 8% 15% 26% 17% 2	1598
	21st to end	Night	33% 6% 11% 25% 21% 4	1957
September	1st to 10th	Night	32% 7% 13% 26% 18% 3	1818
	11th to 20th	Night	32% 5% 9% 32% 20% 1	1980
	21st to end	Night	40% 6% 11% 26% 16% 1	1980
October	1st to 10th	Night	40% 6% 10% 25% 17% 1	1980
	11th to 20th	Night	52% 6% 10% 21% 11% 1	2183
	21st to end	Night	56% 5% 10% 19% 9% 1	2574
November	1st to 10th	Night	47% 6% 10% 22% 14% 1	2406
	11th to 20th	Night	58% 6% 12% 15% 7% 1	2470
	21st to end	Night	60% 6% 13% 17% 3	2470
December	1st to 10th	Night	71% 6% 9% 11% 5%	2561
	11th to 20th	Night	70% 6% 10% 10% 3	3281
	21st to end	Night	75% 6% 10% 6% 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	23% 21% 33% 18% 5% 1	270
	11th to 20th	Day	25% 21% 40% 10% 4	270
	21st to end	Day	25% 21% 34% 18% 2	297
February	1st to 10th	Day	26% 24% 30% 15% 3 1	270
	11th to 20th	Day	26% 24% 35% 14% 1	270
	21st to end	Day	25% 35% 29% 9% 1	225
March	1st to 10th	Day	21% 29% 36% 10% 3	270
	11th to 20th	Day	20% 21% 34% 19% 6%	405
	21st to end	Day	29% 19% 31% 16% 4 1	490
April	1st to 10th	Day	27% 16% 32% 19% 5%	420
	11th to 20th	Day	26% 24% 25% 15% 8% 2	412
	21st to end	Day	26% 18% 32% 16% 8% 1	420
May	1st to 10th	Day	23% 20% 29% 18% 8% 2	423
	11th to 20th	Day	21% 13% 30% 22% 9% 4	447
	21st to end	Day	14% 12% 28% 26% 16% 4	638
June	1st to 10th	Day	12% 10% 35% 28% 11% 4	630
	11th to 20th	Day	14% 10% 30% 29% 14% 3	630
	21st to end	Day	12% 12% 33% 28% 12% 4	630
July	1st to 10th	Day	7% 6% 26% 30% 21% 9%	621
	11th to 20th	Day	12% 7% 29% 28% 18% 7%	618
	21st to end	Day	8% 5% 28% 32% 20% 6%	680
August	1st to 10th	Day	9% 5% 21% 27% 23% 15%	446
	11th to 20th	Day	11% 5% 26% 25% 25% 8%	439
	21st to end	Day	12% 6% 24% 29% 22% 7%	495
September	1st to 10th	Day	14% 8% 24% 28% 19% 7%	450
	11th to 20th	Day	8% 8% 22% 26% 28% 8%	450
	21st to end	Day	15% 14% 23% 26% 16% 6%	450
October	1st to 10th	Day	19% 12% 27% 22% 15% 5%	450
	11th to 20th	Day	25% 20% 28% 22% 5%	375
	21st to end	Day	31% 21% 34% 11% 3	297
November	1st to 10th	Day	18% 20% 34% 21% 6% 1	270
	11th to 20th	Day	25% 26% 28% 16% 4	270
	21st to end	Day	30% 19% 39% 11% 2	270
December	1st to 10th	Day	25% 34% 22% 14% 4	270
	11th to 20th	Day	21% 27% 36% 14% 2	270
	21st to end	Day	22% 31% 34% 11% 2	297
January	1st to 10th	Night	23% 17% 33% 21% 5%	950
	11th to 20th	Night	25% 16% 35% 21% 3 1	950
	21st to end	Night	22% 13% 37% 25% 3	1041
February	1st to 10th	Night	24% 15% 37% 20% 4	760
	11th to 20th	Night	20% 18% 34% 24% 3	743
	21st to end	Night	24% 19% 37% 17% 3	628
March	1st to 10th	Night	21% 16% 33% 23% 6%	760
	11th to 20th	Night	17% 15% 39% 23% 6%	760
	21st to end	Night	24% 13% 31% 25% 7%	766
April	1st to 10th	Night	17% 16% 34% 26% 6% 1	540
	11th to 20th	Night	23% 13% 35% 24% 5% 1	533
	21st to end	Night	22% 10% 36% 25% 7% 1	540
May	1st to 10th	Night	21% 9% 35% 28% 7% 1	540
	11th to 20th	Night	22% 8% 28% 31% 10%	531
	21st to end	Night	15% 4 31% 32% 17% 1	584
June	1st to 10th	Night	11% 5% 30% 39% 15%	540
	11th to 20th	Night	14% 5% 27% 39% 14% 1	540
	21st to end	Night	11% 4 24% 39% 20% 2	540
July	1st to 10th	Night	8% 3 20% 37% 28% 4	525
	11th to 20th	Night	9% 3 21% 41% 22% 4	522
	21st to end	Night	7% 3 18% 44% 26% 1	591
August	1st to 10th	Night	9% 2 15% 43% 27% 4	537
	11th to 20th	Night	9% 2 16% 41% 28% 4	534
	21st to end	Night	10% 3 20% 35% 29% 3	594
September	1st to 10th	Night	11% 4 21% 36% 23% 4	558
	11th to 20th	Night	12% 4 19% 35% 26% 4	720
	21st to end	Night	16% 10% 23% 29% 19% 4	720
October	1st to 10th	Night	18% 8% 24% 30% 18% 1	720
	11th to 20th	Night	23% 14% 30% 26% 7% 1	720
	21st to end	Night	29% 14% 31% 19% 6%	792
November	1st to 10th	Night	21% 14% 30% 25% 9%	740
	11th to 20th	Night	23% 19% 33% 20% 4 1	760
	21st to end	Night	25% 13% 36% 23% 3	760
December	1st to 10th	Night	27% 18% 34% 18% 4	851
	11th to 20th	Night	25% 16% 38% 18% 3	950
	21st to end	Night	32% 18% 34% 15% 1	1045

Page generated at 2024-03-24 23:37:02. Version ac07

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