Streator
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Streator clear sky chart from 2005-11-06 to 2024-11-04.

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 4 4 6% 7% 37%	101318
	Night	13% 9% 4 7% 5% 4 4 3 5% 7% 38%	97766
Transparency	Day	43% 6% 12% 23% 14% 2	104896
	Night	44% 6% 11% 22% 15% 2	102329
Seeing	Day	16% 10% 28% 26% 15% 5%	15772
	Night	17% 10% 31% 30% 12% 1	25596

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	13% 12% 8% 14% 6% 5% 4 3 4 5% 25%	2527
	11th to 20th	Day	12% 13% 5% 15% 7% 7% 5% 5% 8% 4 18%	2530
	21st to end	Day	18% 20% 9% 12% 6% 4 3 2 4 5% 17%	2979
February	1st to 10th	Day	17% 13% 5% 9% 6% 5% 4 3 4 5% 28%	1725
	11th to 20th	Day	14% 10% 4 8% 6% 5% 4 4 5% 6% 33%	1848
	21st to end	Day	14% 14% 7% 10% 5% 4 4 3 4 6% 30%	1570
March	1st to 10th	Day	17% 15% 4 8% 4 4 3 2 4 5% 34%	3120
	11th to 20th	Day	9% 7% 3 7% 4 5% 5% 5% 6% 8% 40%	3310
	21st to end	Day	20% 12% 5% 10% 5% 5% 5% 4 5% 6% 22%	4155
April	1st to 10th	Day	16% 13% 4 8% 4 4 3 3 5% 5% 34%	2280
	11th to 20th	Day	16% 10% 3 7% 4 4 4 3 4 6% 38%	2254
	21st to end	Day	20% 8% 3 7% 5% 4 5% 3 5% 7% 33%	2323
May	1st to 10th	Day	17% 8% 3 7% 5% 4 5% 4 6% 9% 34%	4082
	11th to 20th	Day	16% 8% 2 6% 4 4 5% 4 5% 8% 40%	4330
	21st to end	Day	11% 5% 2 6% 4 4 5% 4 6% 8% 44%	4824
June	1st to 10th	Day	9% 5% 2 5% 5% 4 5% 4 7% 9% 45%	2660
	11th to 20th	Day	8% 5% 2 6% 5% 5% 5% 5% 7% 8% 45%	2660
	21st to end	Day	10% 6% 3 6% 6% 5% 5% 5% 6% 8% 40%	2660
July	1st to 10th	Day	10% 8% 3 7% 5% 5% 6% 5% 8% 9% 34%	4440
	11th to 20th	Day	7% 5% 2 5% 3 3 5% 4 7% 11% 49%	4440
	21st to end	Day	8% 6% 2 7% 5% 5% 5% 5% 7% 9% 42%	4813
August	1st to 10th	Day	7% 5% 2 6% 4 5% 5% 4 7% 10% 45%	4242
	11th to 20th	Day	9% 6% 2 5% 4 4 5% 4 8% 10% 43%	3729
	21st to end	Day	6% 5% 2 6% 4 4 4 4 7% 10% 48%	4180
September	1st to 10th	Day	11% 5% 1 5% 4 4 4 4 5% 8% 49%	2280
	11th to 20th	Day	11% 4 1 4 3 3 4 5% 6% 7% 52%	2188
	21st to end	Day	9% 7% 3 6% 4 5% 4 3 6% 8% 45%	2090
October	1st to 10th	Day	11% 7% 2 6% 5% 4 4 3 5% 7% 48%	1996
	11th to 20th	Day	16% 8% 3 6% 4 3 4 3 4 6% 43%	1900
	21st to end	Day	19% 8% 3 7% 4 3 4 3 5% 5% 38%	1919
November	1st to 10th	Day	11% 8% 2 5% 4 4 3 3 5% 7% 48%	1699
	11th to 20th	Day	17% 12% 4 7% 4 4 3 3 4 6% 36%	1710
	21st to end	Day	18% 11% 4 8% 5% 3 3 3 5% 4 36%	1634
December	1st to 10th	Day	15% 13% 5% 9% 6% 4 4 3 4 4 33%	1520
	11th to 20th	Day	14% 14% 4 11% 6% 5% 4 3 5% 7% 28%	1918
	21st to end	Day	22% 19% 9% 14% 5% 3 3 2 3 4 14%	2783
January	1st to 10th	Night	14% 15% 6% 10% 5% 4 4 3 4 5% 30%	4428
	11th to 20th	Night	14% 18% 7% 13% 5% 4 5% 4 7% 4 20%	4440
	21st to end	Night	22% 17% 7% 10% 5% 3 3 3 4 4 22%	4683
February	1st to 10th	Night	16% 13% 4 9% 5% 4 4 2 4 6% 32%	2452
	11th to 20th	Night	13% 11% 3 8% 6% 5% 4 3 5% 6% 36%	2218
	21st to end	Night	17% 11% 5% 8% 4 4 3 3 4 6% 34%	1884
March	1st to 10th	Night	17% 12% 3 6% 4 3 3 3 4 5% 39%	3733
	11th to 20th	Night	11% 7% 3 6% 5% 4 4 3 5% 7% 46%	3679
	21st to end	Night	20% 10% 5% 11% 6% 5% 4 3 5% 5% 25%	3475
April	1st to 10th	Night	15% 10% 3 6% 5% 4 3 3 6% 7% 38%	1900
	11th to 20th	Night	18% 8% 2 5% 3 4 3 3 5% 6% 42%	1875
	21st to end	Night	18% 7% 3 6% 4 4 4 4 6% 8% 37%	1855
May	1st to 10th	Night	17% 8% 3 7% 5% 4 4 4 7% 8% 31%	2813
	11th to 20th	Night	13% 6% 2 6% 4 4 4 4 7% 9% 39%	2568
	21st to end	Night	10% 6% 2 6% 5% 5% 5% 4 6% 8% 44%	2743
June	1st to 10th	Night	9% 5% 2 5% 4 4 4 3 5% 9% 49%	1520
	11th to 20th	Night	8% 5% 2 6% 4 5% 4 4 8% 10% 45%	1520
	21st to end	Night	8% 6% 2 6% 5% 6% 5% 4 6% 8% 43%	1520
July	1st to 10th	Night	11% 6% 2 7% 5% 5% 5% 4 6% 9% 41%	2530
	11th to 20th	Night	5% 4 2 4 3 3 5% 3 5% 7% 58%	2530
	21st to end	Night	5% 6% 3 7% 5% 4 5% 5% 7% 9% 46%	2750
August	1st to 10th	Night	6% 4 2 5% 4 4 5% 4 7% 9% 51%	2688
	11th to 20th	Night	6% 5% 2 5% 5% 4 5% 4 7% 9% 49%	3100
	21st to end	Night	6% 4 2 5% 4 3 4 3 6% 10% 53%	3476
September	1st to 10th	Night	11% 5% 2 4 4 3 3 2 3 8% 55%	1900
	11th to 20th	Night	8% 5% 1 4 3 4 4 3 6% 7% 55%	1971
	21st to end	Night	9% 5% 2 6% 4 5% 4 4 6% 8% 46%	2090
October	1st to 10th	Night	10% 5% 2 6% 4 4 4 3 4 6% 54%	2180
	11th to 20th	Night	15% 7% 2 6% 3 3 3 3 4 6% 48%	2280
	21st to end	Night	18% 9% 3 6% 4 4 3 3 5% 6% 39%	2677
November	1st to 10th	Night	10% 8% 2 5% 4 4 4 4 5% 6% 50%	2452
	11th to 20th	Night	13% 10% 3 8% 5% 4 4 3 6% 6% 39%	2470
	21st to end	Night	17% 9% 3 7% 5% 4 3 3 4 5% 39%	2543
December	1st to 10th	Night	16% 11% 4 9% 5% 5% 4 3 4 6% 34%	2660
	11th to 20th	Night	15% 13% 6% 9% 5% 4 3 3 4 5% 33%	3279
	21st to end	Night	22% 18% 7% 11% 6% 5% 4 3 4 4 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 11% 17% 6% 1	2528
	11th to 20th	Day	65% 5% 9% 12% 8% 1	2530
	21st to end	Day	71% 3 8% 12% 5%	2979
February	1st to 10th	Day	58% 5% 11% 17% 7% 2	1725
	11th to 20th	Day	50% 5% 13% 21% 10% 1	1858
	21st to end	Day	56% 5% 10% 21% 6% 2	1570
March	1st to 10th	Day	53% 5% 10% 19% 12% 2	3120
	11th to 20th	Day	39% 7% 14% 26% 14% 1	3310
	21st to end	Day	59% 8% 15% 15% 3	4155
April	1st to 10th	Day	50% 5% 11% 21% 12%	2280
	11th to 20th	Day	47% 6% 9% 23% 12% 4	2254
	21st to end	Day	50% 6% 12% 18% 12% 2	2323
May	1st to 10th	Day	45% 8% 11% 25% 10%	4120
	11th to 20th	Day	42% 7% 10% 31% 10%	4334
	21st to end	Day	34% 8% 12% 21% 21% 5%	4837
June	1st to 10th	Day	34% 8% 13% 26% 17% 3	2660
	11th to 20th	Day	34% 8% 10% 22% 22% 4	2660
	21st to end	Day	39% 8% 13% 22% 15% 3	2660
July	1st to 10th	Day	42% 8% 14% 23% 11% 2	4371
	11th to 20th	Day	27% 9% 17% 30% 17% 1	4365
	21st to end	Day	36% 9% 17% 18% 17% 3	4662
August	1st to 10th	Day	30% 8% 18% 28% 14% 1	4227
	11th to 20th	Day	33% 7% 15% 28% 16% 1	3765
	21st to end	Day	30% 7% 13% 29% 17% 3	4179
September	1st to 10th	Day	34% 5% 12% 24% 20% 5%	2280
	11th to 20th	Day	30% 6% 11% 28% 22% 4	2188
	21st to end	Day	36% 7% 10% 25% 20% 2	2090
October	1st to 10th	Day	25% 4 8% 27% 34% 2	3321
	11th to 20th	Day	29% 3 11% 23% 31% 2	3140
	21st to end	Day	41% 4 9% 24% 18% 3	3144
November	1st to 10th	Day	36% 5% 14% 26% 17% 3	1699
	11th to 20th	Day	49% 5% 11% 23% 12% 1	1710
	21st to end	Day	51% 5% 11% 22% 10%	1634
December	1st to 10th	Day	55% 4 12% 20% 8% 1	1520
	11th to 20th	Day	56% 5% 10% 21% 6% 1	1915
	21st to end	Day	74% 5% 8% 9% 4	2783
January	1st to 10th	Night	56% 6% 12% 18% 9%	4428
	11th to 20th	Night	66% 4 10% 12% 8%	4440
	21st to end	Night	66% 5% 9% 14% 6%	4683
February	1st to 10th	Night	55% 4 11% 18% 11% 2	2452
	11th to 20th	Night	49% 5% 11% 22% 12% 1	2219
	21st to end	Night	52% 4 11% 19% 11% 3	1884
March	1st to 10th	Night	47% 6% 11% 23% 11% 2	3733
	11th to 20th	Night	37% 6% 10% 27% 18% 2	3679
	21st to end	Night	59% 7% 10% 18% 5% 1	3475
April	1st to 10th	Night	45% 5% 11% 22% 13% 2	1900
	11th to 20th	Night	43% 4 9% 23% 15% 5%	1875
	21st to end	Night	44% 7% 13% 21% 12% 4	1855
May	1st to 10th	Night	47% 7% 12% 20% 11% 2	2840
	11th to 20th	Night	38% 10% 15% 26% 10% 1	2569
	21st to end	Night	34% 8% 13% 20% 20% 4	2751
June	1st to 10th	Night	32% 8% 13% 25% 19% 4	1520
	11th to 20th	Night	32% 6% 14% 23% 22% 3	1520
	21st to end	Night	37% 9% 14% 21% 15% 4	1520
July	1st to 10th	Night	40% 7% 14% 22% 13% 3	2490
	11th to 20th	Night	24% 7% 13% 28% 25% 2	2482
	21st to end	Night	32% 9% 16% 18% 19% 5%	2662
August	1st to 10th	Night	26% 8% 19% 27% 18% 1	2679
	11th to 20th	Night	29% 8% 16% 28% 19% 1	3130
	21st to end	Night	28% 7% 12% 33% 18% 3	3476
September	1st to 10th	Night	30% 5% 10% 25% 24% 5%	1900
	11th to 20th	Night	28% 5% 10% 28% 25% 5%	1971
	21st to end	Night	35% 7% 11% 25% 19% 3	2090
October	1st to 10th	Night	21% 4 7% 32% 33% 3	3635
	11th to 20th	Night	28% 4 9% 23% 33% 3	3779
	21st to end	Night	38% 4 9% 25% 20% 4	4402
November	1st to 10th	Night	35% 6% 10% 26% 19% 4	2452
	11th to 20th	Night	46% 5% 12% 21% 14% 2	2470
	21st to end	Night	47% 4 10% 25% 12% 1	2543
December	1st to 10th	Night	52% 5% 12% 21% 9% 1	2660
	11th to 20th	Night	54% 5% 10% 21% 10% 1	3281
	21st to end	Night	72% 6% 8% 10% 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% 15% 32% 24% 7% 1	270
	11th to 20th	Day	25% 17% 37% 13% 7% 1	270
	21st to end	Day	19% 17% 34% 22% 8%	297
February	1st to 10th	Day	24% 13% 39% 20% 4	270
	11th to 20th	Day	21% 16% 37% 19% 7%	270
	21st to end	Day	20% 18% 44% 14% 3	225
March	1st to 10th	Day	24% 19% 37% 16% 3	270
	11th to 20th	Day	24% 17% 37% 17% 5% 1	270
	21st to end	Day	28% 16% 34% 14% 6% 2	496
April	1st to 10th	Day	23% 13% 35% 22% 6% 1	460
	11th to 20th	Day	20% 17% 31% 19% 11% 2	452
	21st to end	Day	23% 12% 34% 22% 8% 2	460
May	1st to 10th	Day	20% 14% 32% 22% 9% 3	463
	11th to 20th	Day	21% 10% 27% 26% 13% 3	632
	21st to end	Day	15% 9% 29% 24% 15% 8%	734
June	1st to 10th	Day	9% 6% 27% 31% 20% 6%	680
	11th to 20th	Day	9% 5% 28% 35% 19% 4	680
	21st to end	Day	12% 8% 33% 29% 15% 4	680
July	1st to 10th	Day	10% 4 18% 30% 22% 15%	671
	11th to 20th	Day	9% 4 21% 31% 23% 11%	668
	21st to end	Day	8% 3 19% 37% 24% 8%	739
August	1st to 10th	Day	7% 3 18% 36% 25% 11%	645
	11th to 20th	Day	10% 4 18% 28% 28% 12%	479
	21st to end	Day	6% 3 17% 33% 29% 12%	539
September	1st to 10th	Day	12% 5% 18% 31% 26% 7%	490
	11th to 20th	Day	10% 3 14% 30% 29% 13%	490
	21st to end	Day	12% 10% 25% 26% 20% 7%	490
October	1st to 10th	Day	16% 5% 27% 31% 18% 4	396
	11th to 20th	Day	16% 21% 31% 22% 8% 1	300
	21st to end	Day	31% 13% 30% 20% 5% 1	330
November	1st to 10th	Day	13% 14% 38% 23% 8% 4	279
	11th to 20th	Day	23% 18% 34% 17% 7% 1	270
	21st to end	Day	23% 12% 37% 23% 6%	270
December	1st to 10th	Day	16% 19% 38% 18% 8% 2	270
	11th to 20th	Day	17% 16% 37% 26% 4	270
	21st to end	Day	24% 21% 39% 13% 2	297
January	1st to 10th	Night	19% 13% 39% 23% 5%	950
	11th to 20th	Night	21% 14% 40% 19% 5%	950
	21st to end	Night	22% 12% 35% 27% 4	1045
February	1st to 10th	Night	23% 11% 39% 23% 4	932
	11th to 20th	Night	19% 14% 36% 27% 3	743
	21st to end	Night	24% 15% 38% 19% 4	628
March	1st to 10th	Night	20% 17% 36% 22% 5%	760
	11th to 20th	Night	17% 12% 37% 27% 5% 1	691
	21st to end	Night	25% 10% 37% 21% 6% 1	627
April	1st to 10th	Night	19% 14% 37% 25% 5%	570
	11th to 20th	Night	21% 13% 32% 27% 6%	563
	21st to end	Night	22% 11% 33% 27% 7% 1	570
May	1st to 10th	Night	19% 8% 36% 29% 8% 1	570
	11th to 20th	Night	17% 7% 31% 34% 10% 1	561
	21st to end	Night	12% 4 30% 36% 16% 1	617
June	1st to 10th	Night	11% 3 27% 46% 13% 1	570
	11th to 20th	Night	11% 4 27% 43% 15% 1	570
	21st to end	Night	9% 3 31% 39% 18%	570
July	1st to 10th	Night	8% 3 17% 37% 31% 4	555
	11th to 20th	Night	7% 2 18% 43% 28% 2	552
	21st to end	Night	4 1 15% 50% 27% 2	624
August	1st to 10th	Night	6% 2 15% 44% 29% 4	567
	11th to 20th	Night	8% 2 13% 40% 32% 4	564
	21st to end	Night	7% 2 16% 41% 32% 2	627
September	1st to 10th	Night	12% 4 19% 35% 28% 3	570
	11th to 20th	Night	9% 4 19% 38% 27% 4	641
	21st to end	Night	10% 8% 25% 34% 22% 1	760
October	1st to 10th	Night	11% 6% 27% 36% 18% 1	760
	11th to 20th	Night	18% 12% 33% 25% 12% 1	760
	21st to end	Night	23% 12% 33% 24% 7%	836
November	1st to 10th	Night	15% 11% 40% 24% 10% 1	755
	11th to 20th	Night	18% 14% 35% 25% 7%	760
	21st to end	Night	21% 12% 36% 25% 6%	833
December	1st to 10th	Night	21% 13% 39% 23% 5%	950
	11th to 20th	Night	21% 12% 35% 26% 5%	950
	21st to end	Night	29% 15% 34% 20% 2	1045

Page generated at 2024-11-01 21:47:36. Version ac07

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