Bemidji State University
Clear Sky Chart
History

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

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	12% 9% 4 8% 6% 5% 5% 4 6% 7% 35%	101779
	Night	11% 10% 4 9% 6% 5% 5% 4 6% 6% 33%	97363
Transparency	Day	48% 4 13% 25% 9% 1	101520
	Night	50% 4 13% 23% 9% 1	97242
Seeing	Day	16% 11% 31% 26% 13% 3	16144
	Night	15% 10% 32% 31% 11% 1	26021

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	6% 13% 6% 17% 9% 7% 5% 4 5% 7% 21%	2218
	11th to 20th	Day	5% 10% 5% 14% 12% 11% 9% 7% 6% 5% 15%	2220
	21st to end	Day	6% 13% 12% 19% 8% 6% 5% 4 4 6% 17%	3028
February	1st to 10th	Day	9% 12% 5% 12% 8% 5% 5% 5% 7% 6% 25%	1710
	11th to 20th	Day	7% 12% 4 10% 7% 7% 6% 3 6% 7% 30%	1664
	21st to end	Day	7% 13% 5% 11% 7% 8% 5% 4 6% 7% 29%	1418
March	1st to 10th	Day	11% 12% 4 8% 6% 5% 5% 4 5% 6% 35%	3373
	11th to 20th	Day	8% 9% 4 13% 6% 4 3 3 6% 8% 35%	3480
	21st to end	Day	16% 15% 5% 11% 5% 4 4 3 4 5% 28%	3814
April	1st to 10th	Day	15% 11% 3 9% 6% 5% 5% 3 6% 5% 31%	2256
	11th to 20th	Day	16% 12% 4 8% 5% 6% 4 4 5% 6% 30%	2410
	21st to end	Day	19% 11% 3 8% 5% 4 4 4 5% 6% 31%	2470
May	1st to 10th	Day	19% 10% 2 6% 4 4 5% 3 6% 6% 35%	4291
	11th to 20th	Day	15% 7% 3 7% 5% 5% 5% 4 6% 7% 37%	4399
	21st to end	Day	20% 8% 2 6% 4 4 4 3 5% 6% 36%	4947
June	1st to 10th	Day	11% 6% 2 6% 5% 5% 6% 4 6% 9% 38%	2850
	11th to 20th	Day	14% 7% 3 6% 6% 5% 4 4 5% 8% 38%	2850
	21st to end	Day	11% 6% 3 6% 6% 5% 6% 4 8% 10% 36%	2850
July	1st to 10th	Day	7% 5% 2 6% 5% 5% 5% 5% 7% 10% 42%	4750
	11th to 20th	Day	7% 4 2 5% 3 4 5% 5% 7% 11% 48%	4750
	21st to end	Day	7% 5% 2 6% 4 4 5% 5% 7% 9% 46%	4912
August	1st to 10th	Day	10% 5% 3 6% 5% 5% 5% 5% 7% 9% 42%	4104
	11th to 20th	Day	13% 5% 2 5% 4 4 5% 4 6% 8% 43%	4041
	21st to end	Day	15% 6% 2 6% 4 4 4 4 5% 7% 44%	4509
September	1st to 10th	Day	12% 6% 3 6% 4 3 3 3 5% 8% 47%	2280
	11th to 20th	Day	12% 7% 3 7% 5% 4 4 3 6% 6% 42%	2169
	21st to end	Day	16% 9% 3 6% 4 4 4 3 4 7% 40%	2053
October	1st to 10th	Day	18% 10% 3 6% 5% 4 4 3 5% 6% 37%	1900
	11th to 20th	Day	18% 14% 4 6% 3 4 3 3 4 6% 35%	1900
	21st to end	Day	17% 15% 4 9% 6% 3 4 3 5% 7% 27%	1998
November	1st to 10th	Day	12% 15% 6% 9% 6% 4 4 4 5% 5% 30%	1503
	11th to 20th	Day	11% 18% 5% 17% 7% 5% 3 2 4 4 24%	1520
	21st to end	Day	11% 14% 6% 13% 9% 6% 5% 4 5% 6% 22%	1520
December	1st to 10th	Day	10% 14% 6% 13% 9% 6% 5% 5% 6% 7% 20%	1501
	11th to 20th	Day	9% 16% 6% 14% 8% 5% 8% 3 5% 4 22%	1679
	21st to end	Day	19% 15% 6% 13% 8% 5% 4 2 3 5% 19%	2442
January	1st to 10th	Night	6% 12% 5% 16% 9% 7% 6% 4 7% 6% 22%	4737
	11th to 20th	Night	5% 12% 6% 15% 9% 9% 12% 6% 7% 6% 14%	4750
	21st to end	Night	7% 17% 10% 16% 7% 5% 5% 4 6% 6% 18%	4632
February	1st to 10th	Night	6% 11% 4 11% 6% 6% 6% 6% 8% 8% 28%	2470
	11th to 20th	Night	5% 11% 4 11% 6% 6% 7% 5% 7% 8% 30%	2403
	21st to end	Night	8% 12% 4 11% 7% 7% 6% 5% 6% 5% 29%	2041
March	1st to 10th	Night	8% 11% 5% 9% 5% 5% 5% 3 4 7% 38%	3483
	11th to 20th	Night	7% 10% 3 14% 7% 5% 5% 4 5% 5% 34%	3479
	21st to end	Night	16% 17% 6% 12% 4 3 3 3 4 5% 28%	3817
April	1st to 10th	Night	14% 11% 3 9% 4 5% 5% 3 5% 6% 36%	1924
	11th to 20th	Night	17% 12% 4 8% 4 4 3 4 4 5% 36%	1718
	21st to end	Night	18% 9% 4 7% 5% 4 4 3 5% 5% 35%	1710
May	1st to 10th	Night	17% 10% 3 6% 4 4 4 3 5% 7% 38%	2659
	11th to 20th	Night	15% 6% 2 5% 4 4 4 4 6% 7% 43%	2506
	21st to end	Night	19% 8% 3 6% 4 5% 4 3 5% 5% 39%	2637
June	1st to 10th	Night	10% 7% 3 6% 5% 4 6% 4 6% 6% 42%	1330
	11th to 20th	Night	12% 5% 2 6% 4 3 4 4 6% 9% 45%	1330
	21st to end	Night	9% 5% 2 5% 5% 4 5% 4 7% 9% 45%	1330
July	1st to 10th	Night	8% 4 1 4 4 4 5% 4 9% 12% 44%	2220
	11th to 20th	Night	5% 3 1 4 3 3 3 3 6% 9% 61%	2220
	21st to end	Night	6% 4 2 4 4 3 4 3 6% 10% 54%	2648
August	1st to 10th	Night	8% 5% 2 4 4 4 4 4 6% 8% 52%	2836
	11th to 20th	Night	14% 4 2 4 3 3 3 4 6% 8% 48%	2798
	21st to end	Night	11% 6% 2 6% 4 4 3 3 5% 7% 48%	3156
September	1st to 10th	Night	10% 5% 2 6% 3 5% 4 3 6% 6% 50%	1900
	11th to 20th	Night	10% 6% 2 6% 4 3 4 3 5% 7% 49%	2009
	21st to end	Night	14% 8% 2 5% 3 4 4 3 4 7% 47%	2107
October	1st to 10th	Night	16% 8% 3 5% 4 4 5% 4 5% 6% 40%	2280
	11th to 20th	Night	15% 11% 4 8% 5% 4 4 4 5% 6% 36%	2280
	21st to end	Night	17% 14% 4 9% 4 5% 5% 4 5% 5% 29%	2595
November	1st to 10th	Night	12% 13% 5% 9% 6% 4 5% 3 5% 5% 33%	2620
	11th to 20th	Night	12% 16% 6% 13% 7% 5% 4 3 6% 6% 22%	2660
	21st to end	Night	10% 12% 5% 12% 8% 6% 5% 4 6% 6% 26%	2660
December	1st to 10th	Night	8% 14% 6% 13% 10% 8% 7% 5% 6% 6% 18%	2675
	11th to 20th	Night	10% 14% 6% 15% 8% 7% 6% 4 5% 5% 19%	3518
	21st to end	Night	20% 14% 7% 12% 7% 5% 4 3 5% 5% 18%	5225

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	63% 4 9% 19% 5%	2219
	11th to 20th	Day	69% 3 7% 17% 5%	2220
	21st to end	Day	69% 3 8% 14% 6%	3028
February	1st to 10th	Day	57% 3 11% 19% 10%	1710
	11th to 20th	Day	53% 4 12% 19% 11% 1	1673
	21st to end	Day	55% 3 12% 19% 11%	1418
March	1st to 10th	Day	50% 3 10% 27% 10%	3375
	11th to 20th	Day	48% 3 13% 27% 9%	3480
	21st to end	Day	60% 3 9% 23% 5%	3814
April	1st to 10th	Day	54% 4 8% 19% 13% 2	2256
	11th to 20th	Day	54% 3 11% 21% 9% 1	2410
	21st to end	Day	54% 4 11% 22% 9%	2470
May	1st to 10th	Day	49% 4 10% 23% 12% 1	4302
	11th to 20th	Day	46% 3 13% 26% 10% 2	4403
	21st to end	Day	49% 3 10% 30% 7% 1	4947
June	1st to 10th	Day	42% 5% 18% 24% 10% 1	2850
	11th to 20th	Day	45% 5% 13% 26% 11% 1	2850
	21st to end	Day	42% 6% 15% 29% 8%	2850
July	1st to 10th	Day	35% 8% 19% 29% 9%	4676
	11th to 20th	Day	28% 6% 20% 34% 11% 1	4669
	21st to end	Day	33% 6% 17% 35% 8% 1	4756
August	1st to 10th	Day	37% 5% 15% 29% 13% 1	4090
	11th to 20th	Day	38% 5% 17% 32% 8%	4080
	21st to end	Day	40% 5% 18% 28% 9% 1	4508
September	1st to 10th	Day	36% 3 15% 34% 11%	2280
	11th to 20th	Day	42% 3 19% 28% 7%	2169
	21st to end	Day	45% 4 13% 31% 7%	2053
October	1st to 10th	Day	50% 3 15% 23% 8% 1	1900
	11th to 20th	Day	52% 3 12% 23% 11% 1	1900
	21st to end	Day	58% 3 15% 18% 5%	1998
November	1st to 10th	Day	56% 4 12% 17% 9% 1	1503
	11th to 20th	Day	66% 3 10% 13% 8% 1	1520
	21st to end	Day	63% 4 13% 13% 6% 1	1520
December	1st to 10th	Day	62% 3 14% 16% 4	1501
	11th to 20th	Day	66% 3 11% 17% 4	1680
	21st to end	Day	70% 2 5% 17% 5%	2442
January	1st to 10th	Night	61% 3 10% 20% 5%	4737
	11th to 20th	Night	69% 3 10% 12% 4	4750
	21st to end	Night	67% 3 9% 17% 5%	4632
February	1st to 10th	Night	51% 4 13% 23% 9% 1	2470
	11th to 20th	Night	49% 5% 12% 21% 12% 1	2404
	21st to end	Night	55% 3 11% 20% 10% 1	2041
March	1st to 10th	Night	46% 3 14% 24% 11% 2	3494
	11th to 20th	Night	52% 3 10% 23% 11%	3480
	21st to end	Night	62% 3 9% 17% 9% 1	3817
April	1st to 10th	Night	50% 4 8% 24% 14% 1	1924
	11th to 20th	Night	52% 3 8% 21% 15% 1	1718
	21st to end	Night	51% 3 10% 23% 12% 1	1710
May	1st to 10th	Night	47% 3 10% 27% 12% 1	2668
	11th to 20th	Night	41% 3 12% 26% 14% 4	2507
	21st to end	Night	47% 4 10% 28% 10% 1	2638
June	1st to 10th	Night	40% 4 18% 26% 10% 1	1330
	11th to 20th	Night	36% 5% 15% 27% 15% 2	1330
	21st to end	Night	35% 6% 19% 30% 9% 1	1330
July	1st to 10th	Night	31% 8% 22% 28% 11% 1	2185
	11th to 20th	Night	21% 5% 17% 42% 15% 1	2178
	21st to end	Night	26% 5% 20% 36% 11% 1	2565
August	1st to 10th	Night	30% 5% 19% 31% 14% 1	2826
	11th to 20th	Night	33% 5% 17% 35% 9% 1	2825
	21st to end	Night	36% 4 18% 30% 11% 1	3156
September	1st to 10th	Night	34% 4 15% 34% 12% 1	1900
	11th to 20th	Night	35% 4 20% 31% 10%	2009
	21st to end	Night	39% 4 10% 36% 11%	2107
October	1st to 10th	Night	44% 4 13% 28% 10% 1	2280
	11th to 20th	Night	50% 3 11% 27% 9%	2280
	21st to end	Night	56% 3 12% 22% 6%	2595
November	1st to 10th	Night	54% 3 11% 22% 9% 1	2620
	11th to 20th	Night	63% 3 12% 14% 7% 1	2660
	21st to end	Night	57% 5% 15% 17% 6%	2660
December	1st to 10th	Night	64% 4 14% 15% 4	2675
	11th to 20th	Night	65% 3 11% 15% 6% 1	3516
	21st to end	Night	69% 3 9% 13% 6%	5225

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	10% 14% 34% 31% 10% 2	270
	11th to 20th	Day	18% 8% 36% 26% 11% 1	270
	21st to end	Day	11% 9% 40% 24% 12% 3	297
February	1st to 10th	Day	17% 13% 43% 21% 5% 1	270
	11th to 20th	Day	13% 20% 36% 22% 6% 4	270
	21st to end	Day	12% 12% 44% 28% 4	225
March	1st to 10th	Day	14% 17% 36% 26% 6% 1	270
	11th to 20th	Day	14% 8% 42% 20% 13% 3	270
	21st to end	Day	15% 16% 36% 24% 8% 2	297
April	1st to 10th	Day	21% 15% 32% 24% 8% 1	436
	11th to 20th	Day	24% 15% 28% 22% 10% 1	608
	21st to end	Day	24% 9% 31% 22% 13% 1	650
May	1st to 10th	Day	22% 15% 30% 22% 9% 2	653
	11th to 20th	Day	19% 11% 28% 28% 11% 3	675
	21st to end	Day	17% 10% 28% 31% 11% 2	734
June	1st to 10th	Day	13% 12% 29% 29% 15% 3	680
	11th to 20th	Day	15% 12% 35% 25% 11% 2	680
	21st to end	Day	13% 9% 30% 27% 15% 5%	680
July	1st to 10th	Day	9% 7% 23% 30% 23% 8%	671
	11th to 20th	Day	10% 7% 28% 27% 19% 9%	668
	21st to end	Day	7% 6% 27% 29% 22% 8%	739
August	1st to 10th	Day	9% 9% 23% 32% 22% 6%	676
	11th to 20th	Day	15% 5% 23% 32% 17% 8%	665
	21st to end	Day	14% 9% 26% 29% 19% 3	738
September	1st to 10th	Day	13% 8% 30% 30% 17% 2	490
	11th to 20th	Day	12% 11% 30% 31% 14% 2	379
	21st to end	Day	19% 13% 33% 24% 11%	300
October	1st to 10th	Day	20% 11% 34% 23% 9% 3	300
	11th to 20th	Day	23% 8% 38% 26% 4	300
	21st to end	Day	24% 19% 32% 16% 8% 1	330
November	1st to 10th	Day	19% 15% 32% 21% 12% 1	276
	11th to 20th	Day	23% 16% 35% 22% 4	270
	21st to end	Day	23% 17% 33% 24% 3	270
December	1st to 10th	Day	13% 15% 41% 24% 6% 1	270
	11th to 20th	Day	15% 16% 37% 28% 4	270
	21st to end	Day	21% 12% 34% 25% 5% 3	297
January	1st to 10th	Night	12% 13% 34% 29% 10% 3	950
	11th to 20th	Night	15% 9% 38% 30% 7% 1	950
	21st to end	Night	15% 11% 36% 28% 8% 1	1045
February	1st to 10th	Night	12% 12% 34% 31% 10% 1	950
	11th to 20th	Night	11% 15% 39% 25% 9% 2	929
	21st to end	Night	14% 11% 36% 28% 9% 2	785
March	1st to 10th	Night	15% 10% 37% 25% 11% 1	623
	11th to 20th	Night	13% 12% 39% 29% 7% 1	570
	21st to end	Night	20% 10% 28% 27% 14% 2	627
April	1st to 10th	Night	19% 10% 34% 28% 8% 1	570
	11th to 20th	Night	22% 10% 32% 26% 9% 1	563
	21st to end	Night	22% 9% 27% 31% 11%	570
May	1st to 10th	Night	20% 9% 30% 32% 9% 1	570
	11th to 20th	Night	19% 7% 31% 32% 9% 1	561
	21st to end	Night	18% 6% 29% 38% 10%	617
June	1st to 10th	Night	12% 8% 32% 34% 15% 1	570
	11th to 20th	Night	13% 6% 30% 41% 10%	570
	21st to end	Night	11% 6% 26% 39% 17% 1	570
July	1st to 10th	Night	6% 2 22% 45% 22% 2	555
	11th to 20th	Night	8% 4 26% 40% 20% 1	552
	21st to end	Night	6% 3 25% 41% 22% 3	624
August	1st to 10th	Night	7% 3 22% 47% 20% 2	567
	11th to 20th	Night	13% 5% 19% 38% 22% 3	564
	21st to end	Night	11% 7% 28% 33% 19% 2	627
September	1st to 10th	Night	12% 6% 26% 35% 18% 2	570
	11th to 20th	Night	11% 6% 31% 35% 15% 2	570
	21st to end	Night	15% 9% 34% 28% 13% 2	587
October	1st to 10th	Night	20% 10% 32% 29% 9%	760
	11th to 20th	Night	21% 10% 36% 26% 7%	760
	21st to end	Night	24% 11% 34% 26% 5%	914
November	1st to 10th	Night	18% 12% 33% 29% 9% 1	936
	11th to 20th	Night	18% 13% 35% 26% 7% 1	950
	21st to end	Night	16% 14% 40% 24% 5% 1	950
December	1st to 10th	Night	14% 14% 35% 28% 9% 1	950
	11th to 20th	Night	19% 12% 38% 25% 6% 1	950
	21st to end	Night	24% 10% 34% 24% 7% 1	1045

Page generated at 2024-10-31 02:39:26. Version ac07

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