Our Prairie Sky
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Our Prairie Sky clear sky chart from 2005-11-06 to 2024-11-25.

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	13% 9% 3 7% 5% 4 5% 4 6% 7% 37%	101448
	Night	14% 10% 4 8% 5% 4 4 3 5% 6% 38%	98095
Transparency	Day	45% 5% 12% 23% 14% 2	105030
	Night	46% 4 11% 22% 15% 2	102654
Seeing	Day	17% 11% 31% 24% 12% 4	15835
	Night	18% 11% 31% 29% 11% 1	25685

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	14% 13% 8% 11% 5% 5% 5% 4 6% 5% 24%	2527
	11th to 20th	Day	14% 15% 7% 15% 5% 4 4 6% 8% 4 17%	2530
	21st to end	Day	20% 24% 7% 11% 4 3 3 2 4 5% 17%	2847
February	1st to 10th	Day	16% 13% 6% 9% 6% 5% 5% 3 5% 7% 25%	1787
	11th to 20th	Day	14% 11% 5% 7% 6% 6% 3 4 5% 6% 33%	1848
	21st to end	Day	16% 13% 6% 10% 5% 4 4 3 6% 6% 28%	1570
March	1st to 10th	Day	17% 15% 4 7% 4 3 4 3 4 5% 33%	3120
	11th to 20th	Day	10% 8% 3 7% 5% 4 5% 4 7% 8% 39%	3260
	21st to end	Day	18% 11% 7% 12% 6% 5% 5% 4 5% 6% 20%	4165
April	1st to 10th	Day	16% 13% 3 8% 5% 5% 4 3 5% 6% 31%	2280
	11th to 20th	Day	17% 9% 2 6% 5% 5% 4 4 6% 7% 36%	2254
	21st to end	Day	20% 8% 3 6% 4 5% 4 4 5% 7% 34%	2394
May	1st to 10th	Day	17% 8% 3 6% 5% 5% 5% 4 6% 8% 33%	4082
	11th to 20th	Day	14% 7% 2 6% 4 4 4 3 6% 9% 40%	4221
	21st to end	Day	10% 6% 2 6% 4 3 5% 4 6% 9% 45%	4824
June	1st to 10th	Day	10% 5% 2 6% 5% 4 5% 4 6% 8% 45%	2660
	11th to 20th	Day	9% 5% 2 6% 4 5% 5% 5% 6% 8% 46%	2660
	21st to end	Day	10% 6% 2 7% 5% 6% 6% 5% 7% 9% 37%	2660
July	1st to 10th	Day	12% 7% 2 8% 5% 6% 6% 5% 7% 9% 34%	4440
	11th to 20th	Day	7% 4 2 5% 4 4 5% 4 7% 10% 47%	4440
	21st to end	Day	8% 6% 3 7% 5% 5% 5% 5% 7% 9% 41%	4813
August	1st to 10th	Day	8% 5% 2 6% 4 5% 5% 4 6% 8% 47%	4268
	11th to 20th	Day	9% 5% 2 6% 4 4 5% 4 6% 9% 45%	3767
	21st to end	Day	6% 4 2 6% 4 5% 5% 4 6% 9% 48%	4180
September	1st to 10th	Day	11% 5% 2 4 4 4 5% 4 5% 7% 47%	2280
	11th to 20th	Day	12% 5% 1 4 4 2 5% 3 5% 8% 50%	2139
	21st to end	Day	11% 6% 2 5% 5% 4 4 4 6% 9% 42%	2090
October	1st to 10th	Day	12% 6% 2 6% 3 4 4 4 5% 6% 47%	2072
	11th to 20th	Day	18% 8% 2 7% 5% 5% 4 4 5% 7% 36%	1874
	21st to end	Day	19% 10% 4 8% 4 4 4 3 6% 6% 33%	1881
November	1st to 10th	Day	13% 9% 3 5% 4 3 3 3 5% 7% 45%	1762
	11th to 20th	Day	17% 9% 4 8% 5% 3 4 3 5% 7% 35%	1800
	21st to end	Day	17% 11% 4 8% 6% 4 4 3 3 6% 34%	1732
December	1st to 10th	Day	16% 14% 4 10% 6% 5% 5% 3 5% 6% 29%	1520
	11th to 20th	Day	13% 13% 6% 11% 5% 4 5% 4 5% 6% 28%	1918
	21st to end	Day	20% 23% 7% 14% 5% 4 4 3 3 4 13%	2783
January	1st to 10th	Night	15% 15% 7% 11% 6% 4 3 3 4 4 28%	4428
	11th to 20th	Night	15% 19% 7% 13% 5% 5% 5% 5% 6% 4 17%	4440
	21st to end	Night	23% 18% 7% 9% 4 4 3 3 4 4 21%	4816
February	1st to 10th	Night	16% 15% 4 9% 5% 5% 4 3 4 5% 31%	2390
	11th to 20th	Night	14% 11% 4 7% 5% 5% 5% 3 5% 7% 36%	2218
	21st to end	Night	19% 12% 4 8% 4 3 4 3 4 6% 33%	1884
March	1st to 10th	Night	17% 12% 3 7% 4 4 3 2 4 5% 39%	3733
	11th to 20th	Night	10% 7% 3 6% 4 4 4 3 5% 6% 47%	3718
	21st to end	Night	19% 9% 8% 10% 6% 5% 4 4 4 5% 27%	3476
April	1st to 10th	Night	14% 9% 3 7% 4 5% 3 3 6% 8% 38%	1900
	11th to 20th	Night	18% 8% 3 7% 4 4 3 2 5% 6% 39%	1875
	21st to end	Night	17% 8% 3 8% 5% 5% 4 4 5% 6% 36%	1784
May	1st to 10th	Night	17% 9% 2 7% 4 4 4 4 6% 8% 34%	2813
	11th to 20th	Night	15% 7% 2 5% 4 4 4 4 6% 9% 40%	2674
	21st to end	Night	10% 7% 2 7% 5% 4 4 4 6% 6% 44%	2743
June	1st to 10th	Night	9% 4 3 6% 4 4 4 4 5% 7% 50%	1520
	11th to 20th	Night	8% 6% 2 7% 4 4 4 4 6% 9% 46%	1520
	21st to end	Night	10% 6% 2 7% 7% 4 5% 4 6% 8% 42%	1520
July	1st to 10th	Night	10% 5% 3 7% 5% 6% 6% 4 6% 9% 41%	2530
	11th to 20th	Night	7% 4 2 5% 4 4 4 3 6% 7% 55%	2530
	21st to end	Night	5% 4 2 6% 5% 6% 5% 4 7% 9% 46%	2750
August	1st to 10th	Night	7% 4 2 6% 5% 4 6% 4 7% 8% 48%	2663
	11th to 20th	Night	8% 4 2 5% 4 4 5% 4 5% 8% 52%	3059
	21st to end	Night	7% 5% 2 5% 4 3 4 3 5% 8% 52%	3476
September	1st to 10th	Night	11% 5% 2 5% 3 3 4 3 5% 6% 52%	1900
	11th to 20th	Night	9% 4 2 5% 3 4 3 3 6% 8% 54%	2021
	21st to end	Night	10% 5% 3 7% 5% 5% 5% 3 5% 6% 46%	2090
October	1st to 10th	Night	11% 5% 2 6% 4 3 4 3 4 5% 53%	2104
	11th to 20th	Night	17% 7% 2 6% 4 3 3 3 3 6% 46%	2304
	21st to end	Night	21% 8% 3 6% 4 3 3 3 5% 6% 37%	2717
November	1st to 10th	Night	12% 8% 3 5% 4 3 3 3 5% 6% 46%	2536
	11th to 20th	Night	13% 9% 4 9% 5% 5% 5% 3 5% 6% 37%	2600
	21st to end	Night	17% 11% 3 7% 5% 4 4 3 4 6% 36%	2540
December	1st to 10th	Night	16% 12% 3 9% 5% 4 4 3 5% 6% 32%	2660
	11th to 20th	Night	15% 14% 5% 9% 5% 4 4 3 5% 5% 31%	3279
	21st to end	Night	23% 19% 6% 11% 6% 4 4 3 4 5% 16%	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	61% 4 14% 14% 6%	2528
	11th to 20th	Day	67% 3 9% 12% 9% 1	2530
	21st to end	Day	71% 4 7% 13% 5%	2847
February	1st to 10th	Day	58% 4 12% 15% 9% 2	1787
	11th to 20th	Day	52% 4 9% 22% 10% 2	1858
	21st to end	Day	57% 5% 9% 20% 6% 3	1570
March	1st to 10th	Day	54% 4 9% 20% 11% 1	3120
	11th to 20th	Day	42% 4 12% 29% 12% 1	3260
	21st to end	Day	64% 5% 14% 14% 3	4165
April	1st to 10th	Day	53% 4 10% 20% 12%	2280
	11th to 20th	Day	47% 5% 11% 22% 12% 3	2254
	21st to end	Day	51% 5% 13% 18% 11% 2	2394
May	1st to 10th	Day	47% 6% 11% 26% 9%	4120
	11th to 20th	Day	42% 5% 12% 28% 11% 1	4225
	21st to end	Day	35% 5% 11% 22% 22% 4	4837
June	1st to 10th	Day	36% 6% 12% 25% 18% 3	2660
	11th to 20th	Day	35% 5% 12% 25% 20% 3	2660
	21st to end	Day	39% 8% 14% 21% 14% 3	2660
July	1st to 10th	Day	45% 6% 12% 20% 14% 2	4371
	11th to 20th	Day	30% 7% 16% 29% 16% 1	4365
	21st to end	Day	39% 7% 15% 17% 19% 3	4662
August	1st to 10th	Day	34% 6% 15% 29% 15% 1	4253
	11th to 20th	Day	34% 5% 11% 33% 16% 1	3804
	21st to end	Day	32% 6% 13% 27% 20% 3	4179
September	1st to 10th	Day	35% 6% 13% 26% 17% 4	2280
	11th to 20th	Day	32% 5% 10% 27% 22% 4	2139
	21st to end	Day	37% 6% 9% 26% 20% 2	2090
October	1st to 10th	Day	26% 4 7% 31% 31% 2	3449
	11th to 20th	Day	35% 4 12% 24% 24% 1	3090
	21st to end	Day	44% 4 9% 25% 17% 2	3081
November	1st to 10th	Day	38% 5% 14% 25% 16% 2	1762
	11th to 20th	Day	50% 4 12% 21% 12% 1	1800
	21st to end	Day	53% 4 10% 22% 11% 1	1732
December	1st to 10th	Day	58% 4 12% 18% 8%	1520
	11th to 20th	Day	57% 5% 10% 20% 7% 1	1915
	21st to end	Day	76% 4 7% 9% 3	2783
January	1st to 10th	Night	61% 4 11% 16% 8% 1	4428
	11th to 20th	Night	69% 3 11% 11% 6%	4440
	21st to end	Night	68% 3 9% 14% 6%	4816
February	1st to 10th	Night	57% 3 10% 18% 10% 2	2390
	11th to 20th	Night	50% 4 10% 22% 13% 2	2219
	21st to end	Night	54% 4 10% 19% 10% 3	1884
March	1st to 10th	Night	49% 3 12% 24% 9% 3	3733
	11th to 20th	Night	37% 5% 11% 28% 18% 2	3718
	21st to end	Night	59% 5% 11% 19% 6%	3476
April	1st to 10th	Night	44% 5% 13% 23% 13% 2	1900
	11th to 20th	Night	47% 3 8% 21% 17% 4	1875
	21st to end	Night	48% 5% 10% 20% 14% 3	1784
May	1st to 10th	Night	47% 5% 13% 22% 12% 2	2840
	11th to 20th	Night	40% 7% 16% 26% 11%	2675
	21st to end	Night	39% 5% 11% 18% 20% 6%	2751
June	1st to 10th	Night	33% 4 13% 26% 20% 4	1520
	11th to 20th	Night	34% 4 12% 23% 23% 3	1520
	21st to end	Night	38% 8% 14% 21% 15% 4	1520
July	1st to 10th	Night	40% 5% 14% 23% 12% 5%	2490
	11th to 20th	Night	28% 5% 13% 27% 25% 2	2482
	21st to end	Night	33% 6% 17% 19% 20% 5%	2662
August	1st to 10th	Night	32% 6% 17% 28% 16% 1	2654
	11th to 20th	Night	30% 5% 13% 29% 20% 1	3088
	21st to end	Night	30% 5% 11% 32% 18% 3	3476
September	1st to 10th	Night	31% 5% 11% 25% 23% 5%	1900
	11th to 20th	Night	28% 4 9% 27% 28% 4	2021
	21st to end	Night	37% 5% 9% 28% 18% 3	2090
October	1st to 10th	Night	22% 4 7% 34% 31% 3	3507
	11th to 20th	Night	33% 4 7% 25% 29% 2	3827
	21st to end	Night	40% 3 8% 24% 21% 4	4467
November	1st to 10th	Night	39% 4 10% 27% 18% 3	2536
	11th to 20th	Night	48% 3 11% 22% 14% 2	2600
	21st to end	Night	51% 3 11% 23% 11%	2540
December	1st to 10th	Night	54% 4 12% 21% 10% 1	2660
	11th to 20th	Night	56% 4 11% 18% 11% 1	3281
	21st to end	Night	72% 4 8% 11% 4	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	21% 16% 36% 23% 4	270
	11th to 20th	Day	27% 19% 35% 13% 5% 1	270
	21st to end	Day	22% 19% 37% 16% 5%	297
February	1st to 10th	Day	26% 19% 40% 13% 2	270
	11th to 20th	Day	24% 19% 37% 17% 3	270
	21st to end	Day	23% 22% 41% 12% 3	225
March	1st to 10th	Day	23% 23% 37% 15% 1	270
	11th to 20th	Day	25% 18% 35% 16% 5%	313
	21st to end	Day	29% 18% 31% 16% 6% 1	506
April	1st to 10th	Day	26% 16% 29% 22% 7%	460
	11th to 20th	Day	23% 19% 29% 17% 10% 2	452
	21st to end	Day	23% 19% 34% 15% 7% 2	460
May	1st to 10th	Day	22% 15% 32% 21% 8% 2	463
	11th to 20th	Day	20% 9% 33% 22% 12% 3	562
	21st to end	Day	12% 10% 34% 24% 13% 6%	734
June	1st to 10th	Day	11% 8% 32% 31% 13% 5%	680
	11th to 20th	Day	13% 6% 33% 30% 15% 4	680
	21st to end	Day	14% 9% 33% 28% 12% 4	680
July	1st to 10th	Day	10% 5% 25% 28% 19% 13%	671
	11th to 20th	Day	10% 6% 28% 29% 18% 9%	668
	21st to end	Day	8% 4 27% 35% 21% 6%	739
August	1st to 10th	Day	9% 3 21% 33% 24% 11%	586
	11th to 20th	Day	9% 5% 20% 30% 24% 11%	479
	21st to end	Day	8% 2 19% 40% 21% 9%	539
September	1st to 10th	Day	13% 5% 22% 32% 21% 7%	490
	11th to 20th	Day	10% 5% 18% 30% 27% 11%	490
	21st to end	Day	15% 9% 26% 26% 17% 7%	490
October	1st to 10th	Day	15% 9% 28% 27% 16% 4	472
	11th to 20th	Day	21% 19% 31% 20% 7%	300
	21st to end	Day	31% 14% 35% 16% 4	330
November	1st to 10th	Day	19% 15% 37% 19% 7% 3	300
	11th to 20th	Day	24% 17% 36% 15% 6% 1	300
	21st to end	Day	24% 12% 39% 20% 4	282
December	1st to 10th	Day	20% 20% 38% 15% 5% 1	270
	11th to 20th	Day	19% 18% 41% 19% 4	270
	21st to end	Day	27% 21% 39% 12% 2	297
January	1st to 10th	Night	21% 16% 37% 23% 3	950
	11th to 20th	Night	23% 18% 36% 20% 4 1	950
	21st to end	Night	21% 15% 35% 25% 4	1045
February	1st to 10th	Night	25% 13% 37% 22% 3	870
	11th to 20th	Night	21% 15% 35% 26% 3	743
	21st to end	Night	25% 16% 36% 19% 4	628
March	1st to 10th	Night	22% 16% 38% 20% 5%	760
	11th to 20th	Night	17% 14% 39% 24% 6% 1	760
	21st to end	Night	24% 11% 35% 22% 7%	637
April	1st to 10th	Night	19% 14% 38% 24% 5% 1	570
	11th to 20th	Night	21% 14% 33% 24% 8%	563
	21st to end	Night	21% 10% 35% 26% 8% 1	570
May	1st to 10th	Night	19% 8% 34% 29% 9%	570
	11th to 20th	Night	19% 6% 30% 33% 12% 1	561
	21st to end	Night	13% 4 28% 37% 18% 1	617
June	1st to 10th	Night	9% 5% 26% 46% 14%	570
	11th to 20th	Night	10% 5% 31% 38% 14% 1	570
	21st to end	Night	12% 5% 27% 36% 19% 1	570
July	1st to 10th	Night	8% 2 20% 44% 23% 3	555
	11th to 20th	Night	7% 2 23% 38% 27% 3	552
	21st to end	Night	5% 3 18% 47% 25% 2	624
August	1st to 10th	Night	5% 1 16% 45% 30% 4	567
	11th to 20th	Night	8% 3 14% 40% 31% 4	564
	21st to end	Night	7% 2 20% 38% 30% 3	627
September	1st to 10th	Night	13% 3 19% 36% 26% 4	570
	11th to 20th	Night	9% 5% 16% 40% 26% 3	691
	21st to end	Night	11% 6% 26% 33% 20% 3	760
October	1st to 10th	Night	13% 7% 25% 35% 18% 2	760
	11th to 20th	Night	21% 13% 32% 26% 8%	760
	21st to end	Night	25% 14% 31% 22% 7%	836
November	1st to 10th	Night	18% 12% 37% 23% 9% 1	780
	11th to 20th	Night	19% 19% 34% 23% 6%	800
	21st to end	Night	23% 13% 37% 21% 6%	790
December	1st to 10th	Night	22% 15% 37% 21% 4	950
	11th to 20th	Night	23% 14% 36% 23% 3	950
	21st to end	Night	29% 15% 35% 20% 1	1045

Page generated at 2024-11-22 07:02:29. Version ac07

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