Springwater Conservation Area
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Springwater Conservation Area clear sky chart from 2005-11-06 to 2025-02-21.

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	15% 10% 4 9% 5% 5% 5% 4 6% 7% 32%	109280
	Night	15% 11% 4 8% 5% 5% 4 4 5% 7% 32%	109268
Transparency	Day	47% 9% 14% 18% 10% 1	112923
	Night	48% 9% 13% 18% 11% 1	113790
Seeing	Day	17% 10% 27% 26% 15% 5%	15193
	Night	19% 9% 28% 29% 13% 2	24483

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	13% 15% 5% 20% 6% 5% 4 3 4 4 21%	3891
	11th to 20th	Day	12% 21% 8% 18% 9% 7% 4 3 5% 5% 9%	4026
	21st to end	Day	19% 18% 7% 13% 6% 4 4 3 4 5% 17%	4466
February	1st to 10th	Day	16% 16% 5% 11% 8% 6% 5% 3 5% 5% 20%	1800
	11th to 20th	Day	15% 13% 7% 13% 8% 6% 5% 3 4 6% 21%	1753
	21st to end	Day	18% 13% 4 10% 6% 6% 5% 4 6% 5% 23%	1560
March	1st to 10th	Day	21% 12% 5% 10% 6% 4 4 3 4 5% 27%	3367
	11th to 20th	Day	12% 14% 5% 10% 5% 5% 4 3 5% 8% 29%	3480
	21st to end	Day	18% 9% 4 9% 6% 4 4 3 5% 6% 31%	3815
April	1st to 10th	Day	16% 12% 4 8% 6% 4 4 3 6% 7% 30%	2166
	11th to 20th	Day	17% 11% 3 7% 5% 4 4 3 6% 7% 33%	2406
	21st to end	Day	20% 9% 3 8% 4 4 4 3 5% 6% 34%	2470
May	1st to 10th	Day	19% 7% 3 8% 5% 4 5% 4 5% 8% 32%	4108
	11th to 20th	Day	17% 9% 3 7% 5% 4 5% 4 7% 8% 32%	4081
	21st to end	Day	11% 5% 2 6% 4 4 4 4 6% 9% 46%	4837
June	1st to 10th	Day	12% 5% 3 6% 5% 4 5% 5% 7% 8% 40%	2660
	11th to 20th	Day	10% 6% 2 7% 4 4 5% 5% 7% 9% 40%	2756
	21st to end	Day	11% 5% 2 6% 4 4 4 5% 7% 10% 42%	2850
July	1st to 10th	Day	9% 5% 2 6% 4 4 5% 5% 7% 10% 43%	4728
	11th to 20th	Day	10% 5% 2 5% 4 4 5% 4 7% 9% 45%	4130
	21st to end	Day	8% 4 2 6% 5% 5% 6% 5% 7% 10% 43%	4466
August	1st to 10th	Day	16% 5% 2 5% 4 4 5% 5% 7% 8% 39%	4104
	11th to 20th	Day	10% 7% 2 8% 4 5% 6% 5% 8% 10% 36%	4044
	21st to end	Day	8% 6% 2 7% 5% 5% 5% 5% 6% 8% 43%	4447
September	1st to 10th	Day	11% 6% 2 7% 4 5% 5% 4 5% 9% 43%	2238
	11th to 20th	Day	10% 5% 2 5% 5% 4 4 4 6% 8% 47%	2090
	21st to end	Day	17% 7% 3 6% 4 4 6% 3 7% 7% 37%	2090
October	1st to 10th	Day	16% 7% 2 7% 4 4 4 4 6% 7% 38%	1932
	11th to 20th	Day	18% 10% 3 7% 5% 5% 5% 4 5% 7% 31%	1900
	21st to end	Day	23% 11% 3 9% 5% 5% 4 4 4 7% 25%	2076
November	1st to 10th	Day	14% 8% 3 7% 6% 5% 5% 5% 6% 7% 35%	1762
	11th to 20th	Day	16% 12% 4 7% 4 5% 4 4 5% 8% 31%	1635
	21st to end	Day	19% 15% 6% 9% 6% 5% 6% 4 6% 6% 19%	1600
December	1st to 10th	Day	19% 16% 5% 10% 6% 5% 5% 4 6% 7% 17%	2600
	11th to 20th	Day	22% 18% 5% 9% 6% 4 4 3 5% 5% 18%	2986
	21st to end	Day	27% 20% 5% 12% 5% 4 5% 3 4 5% 10%	3960
January	1st to 10th	Night	15% 12% 5% 14% 7% 6% 5% 4 5% 6% 21%	6050
	11th to 20th	Night	12% 17% 7% 16% 8% 6% 6% 4 5% 5% 13%	5859
	21st to end	Night	20% 15% 8% 12% 5% 4 4 3 4 5% 20%	6490
February	1st to 10th	Night	17% 16% 4 11% 7% 4 4 4 5% 5% 23%	2600
	11th to 20th	Night	17% 13% 4 9% 6% 5% 4 4 6% 7% 26%	2533
	21st to end	Night	19% 13% 3 9% 7% 5% 6% 4 5% 6% 24%	1892
March	1st to 10th	Night	19% 10% 4 8% 6% 4 4 3 5% 6% 31%	3472
	11th to 20th	Night	12% 9% 3 8% 5% 5% 5% 3 5% 8% 38%	3479
	21st to end	Night	16% 10% 3 8% 4 4 4 3 4 4 38%	3817
April	1st to 10th	Night	19% 10% 3 6% 5% 4 4 4 5% 7% 34%	2013
	11th to 20th	Night	18% 8% 3 6% 5% 4 4 3 6% 7% 36%	1739
	21st to end	Night	15% 7% 3 7% 5% 5% 6% 4 6% 6% 36%	1710
May	1st to 10th	Night	20% 9% 3 5% 4 3 4 4 5% 7% 37%	2833
	11th to 20th	Night	11% 8% 3 8% 6% 5% 5% 4 6% 8% 36%	2794
	21st to end	Night	11% 5% 2 4 3 4 5% 4 6% 8% 49%	2738
June	1st to 10th	Night	13% 5% 3 5% 4 4 4 4 7% 7% 44%	1520
	11th to 20th	Night	10% 5% 2 4 4 5% 5% 5% 9% 10% 43%	1417
	21st to end	Night	11% 5% 2 4 3 6% 5% 4 5% 8% 46%	1330
July	1st to 10th	Night	7% 5% 2 4 4 4 4 4 6% 10% 50%	2236
	11th to 20th	Night	9% 5% 2 5% 3 3 4 3 6% 9% 51%	2826
	21st to end	Night	6% 4 2 5% 4 5% 5% 4 7% 9% 49%	3087
August	1st to 10th	Night	11% 6% 2 6% 5% 4 5% 4 6% 9% 44%	2825
	11th to 20th	Night	9% 6% 2 6% 4 4 4 3 6% 7% 50%	2785
	21st to end	Night	8% 5% 2 5% 4 5% 4 4 6% 9% 49%	3176
September	1st to 10th	Night	10% 6% 3 6% 4 4 4 4 5% 7% 47%	1938
	11th to 20th	Night	9% 4 1 4 4 4 4 3 5% 7% 54%	2090
	21st to end	Night	16% 5% 2 6% 4 5% 5% 4 6% 6% 40%	2090
October	1st to 10th	Night	13% 6% 2 6% 4 4 4 3 5% 7% 44%	2247
	11th to 20th	Night	17% 9% 2 8% 4 4 4 4 5% 5% 37%	2280
	21st to end	Night	22% 8% 3 8% 4 5% 4 3 5% 7% 31%	2520
November	1st to 10th	Night	15% 7% 3 5% 5% 4 5% 4 7% 7% 41%	2536
	11th to 20th	Night	16% 10% 3 7% 6% 5% 5% 4 6% 6% 31%	2762
	21st to end	Night	22% 12% 3 7% 6% 5% 4 5% 6% 6% 24%	2800
December	1st to 10th	Night	14% 15% 6% 12% 6% 6% 6% 4 6% 7% 18%	4580
	11th to 20th	Night	17% 20% 5% 10% 5% 4 4 4 5% 5% 22%	5208
	21st to end	Night	25% 18% 5% 10% 6% 5% 3 3 5% 5% 15%	6996

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	65% 10% 10% 9% 5%	3892
	11th to 20th	Day	74% 11% 7% 5% 3	4060
	21st to end	Day	68% 8% 12% 6% 5% 1	4466
February	1st to 10th	Day	64% 7% 13% 11% 4 1	1800
	11th to 20th	Day	63% 7% 10% 14% 6%	1762
	21st to end	Day	60% 9% 13% 13% 5% 1	1560
March	1st to 10th	Day	58% 8% 11% 18% 4	3370
	11th to 20th	Day	49% 10% 18% 16% 6% 1	3480
	21st to end	Day	48% 9% 14% 17% 10% 1	3815
April	1st to 10th	Day	50% 8% 12% 19% 11% 1	2166
	11th to 20th	Day	48% 8% 12% 18% 12% 1	2406
	21st to end	Day	48% 8% 13% 17% 12% 2	2470
May	1st to 10th	Day	45% 11% 15% 17% 10% 2	4120
	11th to 20th	Day	45% 13% 16% 17% 7% 1	4085
	21st to end	Day	32% 11% 15% 20% 18% 5%	4837
June	1st to 10th	Day	38% 9% 14% 24% 12% 2	2660
	11th to 20th	Day	36% 10% 16% 20% 16% 2	2756
	21st to end	Day	33% 10% 16% 25% 15% 1	2850
July	1st to 10th	Day	33% 9% 15% 25% 15% 3	4655
	11th to 20th	Day	30% 8% 17% 30% 14% 1	4060
	21st to end	Day	32% 10% 18% 20% 19% 1	4324
August	1st to 10th	Day	38% 9% 17% 22% 13% 1	4091
	11th to 20th	Day	38% 11% 17% 25% 8% 1	4083
	21st to end	Day	34% 10% 16% 28% 12% 1	4447
September	1st to 10th	Day	35% 10% 17% 24% 13% 1	2238
	11th to 20th	Day	31% 8% 17% 28% 15%	2090
	21st to end	Day	44% 8% 15% 22% 11% 1	2090
October	1st to 10th	Day	34% 9% 18% 20% 18% 1	3205
	11th to 20th	Day	38% 8% 15% 24% 15%	3140
	21st to end	Day	47% 8% 18% 22% 6%	3402
November	1st to 10th	Day	45% 10% 15% 20% 7% 2	1762
	11th to 20th	Day	50% 10% 17% 13% 9% 1	1635
	21st to end	Day	64% 10% 13% 10% 3	1600
December	1st to 10th	Day	63% 12% 14% 9% 2	2600
	11th to 20th	Day	66% 9% 13% 7% 5%	2986
	21st to end	Day	74% 9% 9% 6% 2	3960
January	1st to 10th	Night	57% 14% 11% 13% 4	6050
	11th to 20th	Night	68% 11% 10% 8% 3	5900
	21st to end	Night	64% 9% 10% 9% 8%	6490
February	1st to 10th	Night	62% 8% 12% 13% 5%	2600
	11th to 20th	Night	56% 8% 15% 15% 6%	2535
	21st to end	Night	58% 8% 12% 16% 6% 1	1892
March	1st to 10th	Night	52% 7% 15% 20% 6%	3482
	11th to 20th	Night	40% 10% 18% 19% 12% 1	3480
	21st to end	Night	44% 8% 13% 19% 14% 2	3817
April	1st to 10th	Night	49% 7% 12% 18% 13% 2	2013
	11th to 20th	Night	46% 6% 11% 19% 16% 2	1739
	21st to end	Night	44% 8% 12% 19% 14% 3	1710
May	1st to 10th	Night	45% 8% 12% 17% 14% 5%	2840
	11th to 20th	Night	43% 10% 15% 20% 10% 2	2795
	21st to end	Night	29% 10% 13% 21% 24% 3	2739
June	1st to 10th	Night	35% 8% 13% 25% 15% 3	1520
	11th to 20th	Night	33% 9% 15% 23% 18% 2	1417
	21st to end	Night	35% 7% 14% 25% 18% 1	1330
July	1st to 10th	Night	28% 8% 13% 26% 18% 7%	2201
	11th to 20th	Night	29% 7% 14% 31% 17% 2	2773
	21st to end	Night	29% 9% 17% 21% 20% 3	2988
August	1st to 10th	Night	35% 8% 14% 25% 16% 2	2814
	11th to 20th	Night	32% 8% 16% 30% 12% 1	2812
	21st to end	Night	30% 8% 13% 31% 16% 1	3176
September	1st to 10th	Night	36% 7% 14% 25% 16% 2	1938
	11th to 20th	Night	28% 7% 14% 30% 18% 1	2090
	21st to end	Night	43% 8% 12% 23% 12% 1	2090
October	1st to 10th	Night	28% 7% 11% 29% 24% 2	3754
	11th to 20th	Night	41% 6% 15% 22% 16%	3779
	21st to end	Night	38% 7% 17% 25% 12% 1	4144
November	1st to 10th	Night	41% 9% 15% 23% 12% 1	2536
	11th to 20th	Night	50% 11% 14% 16% 8% 1	2762
	21st to end	Night	58% 11% 16% 12% 3 1	2800
December	1st to 10th	Night	62% 11% 16% 8% 2	4580
	11th to 20th	Night	63% 10% 11% 10% 6%	5208
	21st to end	Night	69% 9% 10% 9% 3	6996

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	22% 20% 32% 19% 6% 2	263
	11th to 20th	Day	24% 15% 43% 12% 5% 2	300
	21st to end	Day	25% 16% 34% 20% 4 1	330
February	1st to 10th	Day	19% 20% 40% 17% 4	300
	11th to 20th	Day	25% 18% 36% 19% 2	300
	21st to end	Day	22% 25% 40% 12% 1	225
March	1st to 10th	Day	22% 13% 35% 24% 6%	417
	11th to 20th	Day	18% 14% 35% 27% 5% 1	460
	21st to end	Day	26% 13% 33% 21% 7%	506
April	1st to 10th	Day	18% 12% 37% 25% 8% 1	460
	11th to 20th	Day	22% 14% 30% 20% 10% 4	452
	21st to end	Day	22% 10% 30% 27% 8% 2	460
May	1st to 10th	Day	20% 11% 29% 25% 13% 3	463
	11th to 20th	Day	18% 8% 23% 28% 19% 4	487
	21st to end	Day	12% 4 23% 32% 22% 6%	529
June	1st to 10th	Day	12% 4 30% 35% 16% 3	490
	11th to 20th	Day	10% 7% 22% 37% 20% 4	586
	21st to end	Day	13% 4 28% 34% 18% 3	680
July	1st to 10th	Day	7% 4 20% 32% 27% 9%	653
	11th to 20th	Day	13% 4 22% 29% 22% 10%	484
	21st to end	Day	9% 3 17% 39% 24% 8%	532
August	1st to 10th	Day	9% 3 17% 31% 26% 13%	486
	11th to 20th	Day	11% 4 16% 34% 24% 12%	479
	21st to end	Day	10% 3 17% 33% 27% 9%	539
September	1st to 10th	Day	12% 3 21% 29% 23% 11%	490
	11th to 20th	Day	7% 3 17% 26% 31% 16%	490
	21st to end	Day	16% 9% 24% 26% 17% 7%	490
October	1st to 10th	Day	18% 9% 27% 20% 21% 6%	490
	11th to 20th	Day	19% 13% 30% 27% 8% 2	490
	21st to end	Day	25% 13% 33% 22% 7%	525
November	1st to 10th	Day	16% 20% 30% 23% 9% 2	300
	11th to 20th	Day	24% 21% 29% 18% 6% 2	217
	21st to end	Day	26% 18% 38% 18% 2	200
December	1st to 10th	Day	29% 18% 31% 17% 6% 1	200
	11th to 20th	Day	29% 22% 31% 16% 3	200
	21st to end	Day	26% 19% 37% 15% 4	220
January	1st to 10th	Night	24% 17% 38% 15% 6% 1	800
	11th to 20th	Night	28% 17% 34% 18% 4	800
	21st to end	Night	21% 12% 39% 23% 6%	880
February	1st to 10th	Night	25% 13% 36% 22% 3	800
	11th to 20th	Night	22% 14% 34% 26% 4	783
	21st to end	Night	24% 12% 39% 23% 3	629
March	1st to 10th	Night	20% 8% 38% 27% 7%	760
	11th to 20th	Night	20% 10% 36% 27% 7% 1	760
	21st to end	Night	22% 9% 30% 28% 9% 1	836
April	1st to 10th	Night	22% 10% 33% 29% 6%	760
	11th to 20th	Night	20% 10% 31% 28% 10% 1	615
	21st to end	Night	20% 5% 31% 34% 9% 1	570
May	1st to 10th	Night	19% 6% 25% 32% 16% 1	570
	11th to 20th	Night	16% 3 25% 40% 14% 2	556
	21st to end	Night	13% 2 21% 37% 24% 2	411
June	1st to 10th	Night	15% 3 22% 41% 18% 1	380
	11th to 20th	Night	12% 3 25% 42% 19%	380
	21st to end	Night	11% 4 24% 42% 18% 1	380
July	1st to 10th	Night	6% 2 18% 41% 30% 4	370
	11th to 20th	Night	9% 3 16% 40% 27% 4	539
	21st to end	Night	9% 2 16% 45% 26% 2	624
August	1st to 10th	Night	9% 2 14% 39% 32% 4	567
	11th to 20th	Night	9% 3 15% 33% 36% 4	564
	21st to end	Night	9% 3 18% 39% 27% 4	653
September	1st to 10th	Night	11% 5% 19% 32% 27% 6%	760
	11th to 20th	Night	11% 4 13% 36% 32% 5%	760
	21st to end	Night	16% 6% 23% 32% 17% 6%	760
October	1st to 10th	Night	16% 7% 24% 31% 18% 4	760
	11th to 20th	Night	20% 13% 28% 27% 11% 2	760
	21st to end	Night	23% 11% 32% 28% 6%	836
November	1st to 10th	Night	17% 12% 28% 29% 13% 1	780
	11th to 20th	Night	21% 15% 35% 21% 7% 2	800
	21st to end	Night	27% 13% 33% 21% 6%	800
December	1st to 10th	Night	27% 17% 33% 17% 5% 1	800
	11th to 20th	Night	25% 18% 35% 18% 4	800
	21st to end	Night	29% 13% 33% 23% 2	880

Page generated at 2025-02-18 03:26:31. Version ac07

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