Fishers
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Fishers clear sky chart from 2005-11-06 to 2024-01-22.

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% 9% 4 7% 6% 3 5% 5% 5% 7% 36%	74938
	Night	15% 9% 4 7% 5% 3 4 4 5% 7% 38%	75011
Transparency	Day	46% 7% 12% 21% 12% 2	74645
	Night	46% 6% 11% 21% 14% 2	74825
Seeing	Day	17% 11% 26% 24% 15% 6%	14448
	Night	18% 9% 29% 29% 14% 1	24399

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	17% 15% 6% 8% 6% 4 5% 4 5% 5% 24%	1517
	11th to 20th	Day	18% 14% 8% 10% 7% 3 5% 5% 5% 5% 22%	1520
	21st to end	Day	15% 17% 9% 9% 7% 3 5% 4 4 5% 23%	1668
February	1st to 10th	Day	19% 13% 7% 8% 8% 4 4 4 3 5% 25%	1786
	11th to 20th	Day	15% 11% 5% 10% 7% 4 6% 3 5% 5% 28%	1748
	21st to end	Day	18% 15% 6% 9% 5% 2 3 3 4 5% 30%	1480
March	1st to 10th	Day	17% 12% 4 9% 6% 3 4 4 5% 7% 31%	1800
	11th to 20th	Day	18% 9% 4 7% 7% 3 4 4 4 7% 32%	1916
	21st to end	Day	22% 11% 5% 8% 5% 3 4 3 5% 6% 27%	2261
April	1st to 10th	Day	15% 9% 5% 6% 7% 3 4 4 5% 7% 36%	2160
	11th to 20th	Day	17% 9% 3 5% 6% 3 4 5% 5% 7% 36%	2134
	21st to end	Day	20% 8% 3 7% 5% 3 4 4 4 6% 35%	2323
May	1st to 10th	Day	19% 8% 4 7% 6% 4 6% 5% 5% 6% 32%	2340
	11th to 20th	Day	20% 7% 2 6% 6% 3 4 5% 5% 7% 34%	2301
	21st to end	Day	11% 5% 3 6% 7% 4 7% 7% 7% 8% 36%	2580
June	1st to 10th	Day	11% 6% 2 5% 6% 4 6% 5% 6% 8% 41%	2520
	11th to 20th	Day	10% 5% 1 5% 5% 3 5% 6% 7% 8% 44%	2520
	21st to end	Day	9% 6% 3 5% 6% 4 6% 5% 6% 9% 42%	2520
July	1st to 10th	Day	10% 5% 3 5% 6% 4 6% 6% 7% 11% 38%	2520
	11th to 20th	Day	7% 4 2 4 5% 3 5% 6% 7% 11% 46%	2520
	21st to end	Day	8% 4 2 5% 5% 4 6% 6% 8% 10% 43%	2663
August	1st to 10th	Day	8% 4 2 5% 5% 3 5% 6% 6% 11% 45%	2327
	11th to 20th	Day	9% 5% 2 5% 5% 4 5% 6% 8% 10% 40%	2223
	21st to end	Day	8% 4 2 5% 5% 3 4 6% 6% 9% 46%	2376
September	1st to 10th	Day	11% 6% 2 6% 5% 3 5% 4 5% 8% 44%	2124
	11th to 20th	Day	10% 5% 1 5% 5% 3 4 5% 6% 9% 46%	1980
	21st to end	Day	12% 5% 3 4 4 3 4 4 4 7% 50%	1980
October	1st to 10th	Day	13% 5% 2 6% 5% 3 4 3 5% 7% 46%	1980
	11th to 20th	Day	14% 7% 3 5% 4 3 4 5% 5% 7% 43%	1837
	21st to end	Day	19% 9% 4 7% 4 3 3 5% 6% 7% 33%	1782
November	1st to 10th	Day	9% 7% 2 5% 5% 3 3 4 5% 6% 51%	1672
	11th to 20th	Day	15% 10% 4 7% 6% 3 4 3 5% 6% 35%	1710
	21st to end	Day	19% 9% 4 7% 4 3 3 4 5% 6% 35%	1710
December	1st to 10th	Day	19% 14% 5% 9% 5% 3 4 4 3 6% 27%	1710
	11th to 20th	Day	15% 16% 7% 10% 5% 2 4 3 5% 5% 28%	1947
	21st to end	Day	21% 21% 9% 10% 6% 3 4 3 4 5% 15%	2783
January	1st to 10th	Night	18% 12% 6% 10% 6% 3 4 4 4 5% 27%	2648
	11th to 20th	Night	19% 16% 6% 10% 7% 3 4 3 3 4 24%	2660
	21st to end	Night	16% 13% 7% 10% 6% 3 4 4 4 4 27%	2719
February	1st to 10th	Night	21% 13% 5% 9% 7% 3 4 3 4 5% 26%	2169
	11th to 20th	Night	15% 12% 5% 9% 7% 3 3 4 5% 6% 32%	2098
	21st to end	Night	19% 12% 4 9% 5% 3 5% 4 4 5% 29%	1776
March	1st to 10th	Night	16% 8% 5% 7% 6% 3 5% 4 4 6% 36%	2160
	11th to 20th	Night	15% 9% 3 7% 5% 3 5% 4 5% 7% 37%	2044
	21st to end	Night	20% 10% 4 8% 5% 3 3 4 4 7% 33%	2110
April	1st to 10th	Night	13% 8% 3 5% 5% 3 4 5% 6% 8% 39%	1800
	11th to 20th	Night	18% 7% 2 5% 5% 3 5% 4 5% 7% 41%	1775
	21st to end	Night	18% 8% 3 6% 5% 3 5% 5% 5% 7% 35%	1635
May	1st to 10th	Night	18% 8% 4 7% 6% 3 5% 5% 6% 7% 30%	1620
	11th to 20th	Night	18% 6% 3 6% 5% 3 4 4 6% 7% 39%	1592
	21st to end	Night	9% 4 2 5% 6% 4 6% 5% 6% 12% 41%	1691
June	1st to 10th	Night	8% 6% 3 6% 5% 3 5% 4 6% 7% 49%	1440
	11th to 20th	Night	10% 6% 2 5% 5% 2 5% 4 5% 10% 48%	1440
	21st to end	Night	7% 3 3 4 6% 4 5% 6% 6% 11% 45%	1440
July	1st to 10th	Night	9% 5% 1 4 5% 4 4 5% 7% 12% 45%	1440
	11th to 20th	Night	7% 3 2 4 4 3 3 5% 5% 9% 54%	1440
	21st to end	Night	7% 4 2 5% 5% 4 5% 4 5% 8% 53%	1655
August	1st to 10th	Night	8% 4 1 4 4 3 5% 5% 6% 10% 49%	1611
	11th to 20th	Night	7% 4 2 6% 5% 3 5% 5% 5% 8% 49%	1674
	21st to end	Night	7% 3 2 5% 5% 3 3 4 6% 8% 54%	1980
September	1st to 10th	Night	12% 6% 2 6% 5% 3 4 4 5% 8% 47%	1816
	11th to 20th	Night	8% 4 2 4 4 2 4 4 5% 8% 55%	1980
	21st to end	Night	11% 5% 2 4 4 3 4 4 5% 6% 52%	1980
October	1st to 10th	Night	9% 5% 2 5% 4 3 4 3 5% 7% 53%	1980
	11th to 20th	Night	19% 6% 2 4 4 3 3 4 4 7% 44%	2119
	21st to end	Night	19% 7% 3 5% 5% 3 4 4 4 6% 39%	2574
November	1st to 10th	Night	13% 7% 3 5% 3 2 3 4 5% 6% 49%	2406
	11th to 20th	Night	15% 8% 4 7% 5% 3 4 4 5% 7% 40%	2470
	21st to end	Night	19% 11% 4 7% 6% 3 4 4 4 6% 32%	2470
December	1st to 10th	Night	18% 10% 6% 8% 7% 3 4 4 4 5% 29%	2470
	11th to 20th	Night	17% 13% 6% 8% 6% 3 3 4 4 5% 31%	3245
	21st to end	Night	23% 19% 6% 9% 6% 4 4 4 4 5% 17%	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% 4 10% 16% 8%	1518
	11th to 20th	Day	64% 6% 11% 13% 5%	1520
	21st to end	Day	63% 5% 12% 15% 5% 1	1668
February	1st to 10th	Day	63% 5% 9% 15% 8% 1	1786
	11th to 20th	Day	58% 5% 10% 19% 8% 1	1758
	21st to end	Day	57% 5% 9% 19% 8% 2	1480
March	1st to 10th	Day	53% 6% 10% 22% 9%	1800
	11th to 20th	Day	53% 5% 13% 18% 9% 2	1916
	21st to end	Day	59% 5% 12% 18% 5% 1	2261
April	1st to 10th	Day	48% 7% 12% 20% 13% 1	2160
	11th to 20th	Day	47% 6% 12% 22% 10% 3	2134
	21st to end	Day	51% 6% 11% 20% 10% 3	2323
May	1st to 10th	Day	52% 7% 12% 19% 9% 1	2340
	11th to 20th	Day	50% 8% 11% 17% 13% 1	2305
	21st to end	Day	41% 11% 13% 19% 14% 2	2580
June	1st to 10th	Day	40% 7% 13% 23% 15% 3	2520
	11th to 20th	Day	35% 8% 12% 23% 19% 2	2520
	21st to end	Day	39% 8% 15% 19% 15% 4	2520
July	1st to 10th	Day	39% 9% 15% 20% 14% 3	2451
	11th to 20th	Day	31% 9% 17% 25% 17% 2	2445
	21st to end	Day	33% 10% 18% 22% 14% 3	2515
August	1st to 10th	Day	32% 8% 16% 28% 14% 2	2314
	11th to 20th	Day	37% 8% 15% 25% 14% 1	2223
	21st to end	Day	31% 8% 14% 23% 16% 7%	2376
September	1st to 10th	Day	37% 7% 13% 22% 17% 4	2124
	11th to 20th	Day	33% 7% 13% 24% 19% 3	1980
	21st to end	Day	34% 5% 11% 25% 23% 1	1980
October	1st to 10th	Day	37% 6% 11% 24% 19% 3	1980
	11th to 20th	Day	39% 6% 10% 24% 18% 2	1837
	21st to end	Day	50% 6% 10% 21% 12% 1	1782
November	1st to 10th	Day	34% 5% 13% 27% 17% 4	1672
	11th to 20th	Day	49% 5% 9% 20% 13% 3	1710
	21st to end	Day	52% 4 11% 22% 10% 2	1710
December	1st to 10th	Day	60% 5% 10% 17% 8%	1710
	11th to 20th	Day	59% 5% 9% 21% 5% 1	1944
	21st to end	Day	73% 5% 8% 9% 5%	2783
January	1st to 10th	Night	59% 5% 8% 18% 10%	2648
	11th to 20th	Night	65% 4 9% 15% 6% 1	2660
	21st to end	Night	61% 5% 11% 15% 8% 1	2719
February	1st to 10th	Night	61% 4 12% 15% 7% 1	2169
	11th to 20th	Night	53% 5% 12% 18% 11% 1	2099
	21st to end	Night	57% 5% 11% 16% 9% 2	1776
March	1st to 10th	Night	49% 6% 11% 21% 12% 1	2160
	11th to 20th	Night	46% 6% 13% 22% 11% 3	2044
	21st to end	Night	53% 5% 11% 22% 8% 2	2110
April	1st to 10th	Night	42% 6% 13% 23% 13% 2	1800
	11th to 20th	Night	43% 5% 10% 20% 17% 5%	1775
	21st to end	Night	47% 8% 10% 19% 12% 4	1635
May	1st to 10th	Night	51% 8% 10% 18% 10% 2	1620
	11th to 20th	Night	44% 7% 13% 21% 13% 2	1593
	21st to end	Night	35% 9% 16% 21% 14% 4	1692
June	1st to 10th	Night	34% 7% 11% 25% 20% 3	1440
	11th to 20th	Night	34% 7% 12% 23% 21% 4	1440
	21st to end	Night	31% 10% 16% 23% 16% 4	1440
July	1st to 10th	Night	33% 9% 15% 22% 15% 6%	1400
	11th to 20th	Night	26% 7% 16% 29% 20% 2	1392
	21st to end	Night	29% 7% 14% 29% 17% 4	1563
August	1st to 10th	Night	28% 9% 15% 28% 18% 2	1600
	11th to 20th	Night	31% 8% 14% 26% 19% 2	1674
	21st to end	Night	27% 7% 16% 23% 21% 6%	1980
September	1st to 10th	Night	34% 8% 12% 21% 19% 6%	1816
	11th to 20th	Night	28% 6% 11% 27% 24% 3	1980
	21st to end	Night	33% 6% 11% 23% 24% 4	1980
October	1st to 10th	Night	31% 6% 13% 23% 24% 3	1980
	11th to 20th	Night	41% 4 10% 24% 19% 2	2119
	21st to end	Night	46% 5% 10% 23% 14% 2	2574
November	1st to 10th	Night	36% 5% 11% 24% 22% 3	2406
	11th to 20th	Night	44% 5% 10% 22% 16% 3	2470
	21st to end	Night	54% 4 9% 22% 10%	2470
December	1st to 10th	Night	57% 4 11% 19% 9%	2470
	11th to 20th	Night	55% 4 9% 20% 11% 1	3247
	21st to end	Night	71% 5% 9% 10% 5%	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	24% 20% 31% 21% 3	270
	11th to 20th	Day	23% 21% 36% 14% 6%	270
	21st to end	Day	27% 20% 29% 19% 5%	267
February	1st to 10th	Day	32% 16% 34% 15% 3	240
	11th to 20th	Day	23% 24% 34% 15% 5%	240
	21st to end	Day	26% 19% 42% 12% 1	198
March	1st to 10th	Day	21% 26% 33% 17% 3	240
	11th to 20th	Day	27% 15% 33% 16% 8% 1	356
	21st to end	Day	31% 15% 31% 16% 6% 1	462
April	1st to 10th	Day	15% 18% 36% 19% 9% 2	420
	11th to 20th	Day	20% 17% 27% 21% 12% 2	412
	21st to end	Day	25% 16% 32% 19% 6% 2	420
May	1st to 10th	Day	24% 13% 31% 23% 7% 2	423
	11th to 20th	Day	23% 6% 29% 23% 13% 6%	447
	21st to end	Day	12% 7% 27% 23% 21% 10%	534
June	1st to 10th	Day	11% 6% 30% 29% 19% 6%	630
	11th to 20th	Day	12% 6% 24% 33% 19% 6%	630
	21st to end	Day	12% 7% 26% 29% 18% 7%	630
July	1st to 10th	Day	13% 2 17% 26% 26% 16%	621
	11th to 20th	Day	6% 5% 20% 34% 23% 12%	618
	21st to end	Day	10% 2 17% 31% 28% 11%	604
August	1st to 10th	Day	9% 3 13% 28% 30% 16%	446
	11th to 20th	Day	12% 4 18% 28% 24% 13%	439
	21st to end	Day	8% 3 14% 32% 29% 14%	495
September	1st to 10th	Day	13% 4 15% 31% 27% 10%	450
	11th to 20th	Day	10% 3 15% 28% 28% 16%	450
	21st to end	Day	14% 9% 22% 22% 22% 10%	450
October	1st to 10th	Day	11% 8% 24% 33% 16% 7%	450
	11th to 20th	Day	15% 17% 31% 24% 11%	392
	21st to end	Day	28% 17% 34% 19% 3	297
November	1st to 10th	Day	11% 20% 30% 22% 15% 2	270
	11th to 20th	Day	21% 20% 30% 17% 9% 2	270
	21st to end	Day	25% 12% 37% 22% 4	270
December	1st to 10th	Day	20% 25% 33% 16% 4 1	270
	11th to 20th	Day	21% 19% 35% 18% 6% 1	270
	21st to end	Day	29% 21% 31% 16% 4	297
January	1st to 10th	Night	25% 16% 33% 22% 4	950
	11th to 20th	Night	27% 14% 37% 19% 4	950
	21st to end	Night	24% 15% 34% 24% 3	920
February	1st to 10th	Night	28% 12% 34% 24% 3	720
	11th to 20th	Night	21% 15% 37% 24% 3	703
	21st to end	Night	27% 11% 40% 20% 2	592
March	1st to 10th	Night	20% 16% 35% 24% 6%	720
	11th to 20th	Night	20% 13% 37% 23% 6% 1	720
	21st to end	Night	25% 10% 32% 27% 5% 1	724
April	1st to 10th	Night	17% 12% 36% 27% 8% 1	540
	11th to 20th	Night	19% 11% 31% 29% 9% 1	533
	21st to end	Night	23% 8% 39% 22% 7% 1	540
May	1st to 10th	Night	19% 9% 36% 26% 10%	540
	11th to 20th	Night	21% 5% 24% 32% 17% 1	531
	21st to end	Night	10% 3 24% 37% 23% 2	584
June	1st to 10th	Night	11% 3 24% 45% 16% 1	540
	11th to 20th	Night	10% 4 24% 39% 22% 1	540
	21st to end	Night	7% 3 24% 39% 25% 1	540
July	1st to 10th	Night	10% 2 13% 35% 33% 7%	525
	11th to 20th	Night	7% 3 16% 38% 31% 4	522
	21st to end	Night	8% 2 16% 41% 31% 2	591
August	1st to 10th	Night	8% 1 13% 41% 33% 4	537
	11th to 20th	Night	7% 2 14% 41% 31% 5%	534
	21st to end	Night	7% 1 16% 34% 37% 5%	594
September	1st to 10th	Night	14% 4 14% 33% 31% 4	556
	11th to 20th	Night	9% 3 17% 33% 35% 4	720
	21st to end	Night	13% 5% 21% 33% 25% 3	720
October	1st to 10th	Night	11% 6% 25% 34% 20% 5%	720
	11th to 20th	Night	21% 10% 30% 26% 12%	720
	21st to end	Night	23% 10% 35% 25% 6% 1	792
November	1st to 10th	Night	16% 9% 34% 27% 13% 1	740
	11th to 20th	Night	17% 16% 31% 27% 8% 1	760
	21st to end	Night	26% 12% 28% 27% 7%	760
December	1st to 10th	Night	23% 13% 36% 23% 5%	760
	11th to 20th	Night	25% 11% 34% 23% 6%	916
	21st to end	Night	30% 15% 32% 19% 4	1045

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