Hopewell Rocks Provincial Park
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Hopewell Rocks Provincial Park clear sky chart from 2005-11-06 to 2025-04-11.

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	16% 9% 3 8% 5% 5% 5% 4 6% 7% 32%	113552
	Night	18% 11% 4 8% 5% 4 4 3 5% 6% 33%	114823
Transparency	Day	30% 43% 8% 12% 6% 1	117157
	Night	32% 41% 7% 12% 7% 1	119382
Seeing	Day	24% 20% 32% 18% 6% 1	17393
	Night	24% 17% 31% 21% 6%	25115

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% 16% 4 10% 6% 6% 5% 3 5% 4 27%	3157
	11th to 20th	Day	13% 13% 6% 12% 7% 5% 4 3 4 5% 29%	3535
	21st to end	Day	10% 9% 3 9% 5% 4 6% 4 6% 7% 37%	4466
February	1st to 10th	Day	15% 12% 4 10% 5% 4 5% 3 6% 7% 30%	1800
	11th to 20th	Day	14% 13% 4 8% 5% 5% 5% 4 5% 7% 30%	1753
	21st to end	Day	11% 13% 4 8% 5% 5% 4 4 6% 6% 35%	1495
March	1st to 10th	Day	18% 13% 5% 13% 5% 4 3 3 4 5% 26%	4919
	11th to 20th	Day	14% 10% 4 10% 5% 6% 5% 5% 5% 6% 29%	4980
	21st to end	Day	25% 13% 4 8% 5% 5% 5% 4 5% 5% 22%	5466
April	1st to 10th	Day	19% 12% 4 8% 6% 5% 5% 4 5% 6% 27%	2372
	11th to 20th	Day	17% 11% 3 7% 5% 5% 4 4 5% 6% 33%	2377
	21st to end	Day	22% 9% 2 7% 5% 4 4 3 5% 7% 31%	2470
May	1st to 10th	Day	18% 10% 4 10% 7% 6% 5% 3 5% 6% 25%	4216
	11th to 20th	Day	16% 8% 3 6% 5% 4 4 3 5% 7% 37%	4398
	21st to end	Day	15% 7% 3 8% 6% 6% 5% 5% 7% 9% 28%	4836
June	1st to 10th	Day	23% 8% 3 7% 5% 5% 5% 4 5% 8% 26%	2765
	11th to 20th	Day	20% 7% 3 6% 5% 4 5% 4 6% 8% 33%	2850
	21st to end	Day	24% 9% 3 7% 5% 4 4 4 5% 7% 28%	2850
July	1st to 10th	Day	14% 8% 3 7% 6% 6% 6% 5% 6% 8% 32%	4760
	11th to 20th	Day	13% 6% 2 7% 6% 6% 6% 5% 7% 8% 34%	4614
	21st to end	Day	12% 6% 2 6% 6% 5% 6% 5% 7% 9% 35%	4691
August	1st to 10th	Day	16% 9% 4 8% 5% 5% 5% 4 8% 8% 29%	4105
	11th to 20th	Day	13% 6% 2 6% 5% 5% 6% 4 6% 8% 38%	4045
	21st to end	Day	11% 5% 2 5% 4 5% 5% 4 7% 8% 46%	4415
September	1st to 10th	Day	14% 4 2 5% 4 4 5% 5% 7% 8% 42%	2280
	11th to 20th	Day	15% 7% 3 7% 4 3 4 3 5% 6% 42%	2176
	21st to end	Day	17% 6% 2 6% 3 3 4 3 6% 6% 44%	2049
October	1st to 10th	Day	16% 7% 2 6% 3 4 4 4 5% 8% 40%	1900
	11th to 20th	Day	18% 8% 3 6% 4 4 4 4 5% 6% 38%	1900
	21st to end	Day	18% 8% 2 8% 6% 5% 4 3 4 7% 35%	2071
November	1st to 10th	Day	21% 10% 3 7% 4 4 4 4 4 7% 33%	1587
	11th to 20th	Day	19% 11% 4 7% 4 4 4 3 5% 5% 33%	1600
	21st to end	Day	18% 12% 3 8% 5% 5% 5% 4 5% 4 31%	1600
December	1st to 10th	Day	20% 11% 3 8% 4 4 3 4 4 6% 33%	2610
	11th to 20th	Day	22% 12% 3 7% 4 4 3 2 3 4 35%	2968
	21st to end	Day	16% 13% 5% 9% 5% 4 4 3 5% 6% 30%	3476
January	1st to 10th	Night	13% 15% 5% 10% 5% 5% 4 3 4 5% 31%	6808
	11th to 20th	Night	15% 13% 5% 12% 6% 5% 4 3 4 5% 26%	6357
	21st to end	Night	11% 11% 5% 8% 7% 4 3 2 4 6% 38%	6490
February	1st to 10th	Night	17% 11% 3 8% 5% 5% 4 4 7% 5% 30%	2600
	11th to 20th	Night	15% 14% 4 8% 5% 4 5% 3 5% 6% 30%	2533
	21st to end	Night	12% 13% 5% 9% 4 4 5% 3 5% 5% 34%	2130
March	1st to 10th	Night	25% 14% 4 10% 5% 4 4 2 3 3 25%	4920
	11th to 20th	Night	20% 11% 5% 10% 6% 4 4 3 5% 6% 27%	4979
	21st to end	Night	28% 12% 3 7% 5% 4 4 3 3 4 27%	5466
April	1st to 10th	Night	21% 14% 4 7% 6% 4 4 3 4 5% 27%	2026
	11th to 20th	Night	20% 11% 3 6% 5% 4 3 3 4 6% 34%	1757
	21st to end	Night	22% 10% 3 8% 5% 4 4 4 5% 6% 31%	1710
May	1st to 10th	Night	20% 11% 4 8% 4 5% 5% 4 6% 6% 26%	2726
	11th to 20th	Night	19% 8% 2 6% 4 3 4 3 5% 7% 39%	2506
	21st to end	Night	15% 9% 3 9% 6% 6% 6% 5% 7% 7% 28%	2749
June	1st to 10th	Night	24% 9% 4 7% 5% 5% 4 4 5% 7% 26%	1429
	11th to 20th	Night	19% 7% 3 7% 5% 4 4 4 5% 7% 35%	1330
	21st to end	Night	24% 9% 2 6% 4 6% 5% 4 6% 7% 26%	1330
July	1st to 10th	Night	14% 9% 3 10% 7% 5% 6% 5% 7% 7% 28%	2210
	11th to 20th	Night	13% 7% 2 8% 5% 8% 6% 5% 7% 9% 29%	2320
	21st to end	Night	12% 6% 3 6% 5% 5% 5% 4 6% 8% 38%	2866
August	1st to 10th	Night	16% 8% 3 9% 5% 6% 6% 4 6% 7% 28%	2825
	11th to 20th	Night	10% 5% 2 8% 6% 5% 6% 5% 8% 9% 35%	2782
	21st to end	Night	12% 5% 2 5% 4 4 5% 3 6% 7% 47%	3239
September	1st to 10th	Night	13% 6% 2 6% 4 5% 4 4 5% 8% 43%	1900
	11th to 20th	Night	15% 7% 2 6% 4 3 3 3 4 7% 45%	2000
	21st to end	Night	16% 7% 3 6% 4 3 3 4 5% 5% 43%	2130
October	1st to 10th	Night	19% 7% 3 6% 4 3 3 4 6% 7% 39%	2280
	11th to 20th	Night	18% 7% 3 6% 4 4 4 3 5% 6% 40%	2280
	21st to end	Night	24% 9% 3 6% 4 4 4 3 4 5% 35%	2523
November	1st to 10th	Night	21% 8% 3 7% 4 4 4 2 5% 6% 36%	2709
	11th to 20th	Night	19% 10% 4 8% 4 4 4 3 6% 6% 31%	2800
	21st to end	Night	22% 11% 4 6% 4 4 4 3 5% 6% 32%	2800
December	1st to 10th	Night	15% 11% 3 8% 4 4 3 3 5% 6% 37%	4580
	11th to 20th	Night	22% 13% 3 6% 3 4 3 3 4 5% 35%	5231
	21st to end	Night	21% 13% 5% 8% 4 4 4 3 4 5% 30%	7502

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	45% 28% 9% 12% 5% 1	3158
	11th to 20th	Day	42% 28% 9% 13% 7% 1	3564
	21st to end	Day	35% 30% 8% 11% 12% 4	4466
February	1st to 10th	Day	22% 62% 4 7% 5% 1	1800
	11th to 20th	Day	21% 61% 4 8% 5%	1761
	21st to end	Day	19% 62% 4 7% 6% 2	1495
March	1st to 10th	Day	45% 29% 6% 9% 9% 2	4923
	11th to 20th	Day	42% 32% 12% 10% 4 1	4980
	21st to end	Day	48% 30% 4 12% 5% 1	5466
April	1st to 10th	Day	24% 62% 3 5% 5% 1	2372
	11th to 20th	Day	19% 66% 5% 8% 2	2377
	21st to end	Day	21% 65% 4 5% 4 1	2470
May	1st to 10th	Day	36% 44% 6% 11% 3	4230
	11th to 20th	Day	27% 43% 13% 14% 3	4402
	21st to end	Day	31% 47% 11% 8% 4	4836
June	1st to 10th	Day	19% 65% 4 9% 3	2765
	11th to 20th	Day	17% 66% 6% 8% 3	2850
	21st to end	Day	20% 63% 4 8% 5%	2850
July	1st to 10th	Day	32% 38% 11% 10% 8% 1	4685
	11th to 20th	Day	28% 39% 10% 18% 4	4533
	21st to end	Day	25% 41% 12% 17% 4	4541
August	1st to 10th	Day	34% 40% 7% 16% 2	4092
	11th to 20th	Day	27% 41% 8% 13% 10%	4084
	21st to end	Day	21% 39% 11% 16% 12% 1	4415
September	1st to 10th	Day	13% 62% 7% 11% 6%	2280
	11th to 20th	Day	20% 60% 6% 10% 4	2176
	21st to end	Day	14% 60% 7% 13% 6%	2049
October	1st to 10th	Day	28% 39% 9% 18% 6%	3160
	11th to 20th	Day	25% 38% 6% 23% 8%	3140
	21st to end	Day	25% 38% 10% 14% 13%	3397
November	1st to 10th	Day	25% 57% 6% 8% 3	1587
	11th to 20th	Day	28% 57% 4 6% 4 1	1600
	21st to end	Day	27% 58% 5% 7% 4	1600
December	1st to 10th	Day	31% 37% 8% 19% 5%	2610
	11th to 20th	Day	39% 32% 6% 13% 9% 2	2967
	21st to end	Day	41% 29% 9% 14% 7%	3476
January	1st to 10th	Night	39% 28% 8% 21% 4	6808
	11th to 20th	Night	44% 29% 8% 14% 4	6403
	21st to end	Night	34% 29% 7% 16% 12% 3	6490
February	1st to 10th	Night	24% 62% 4 5% 5% 1	2600
	11th to 20th	Night	22% 61% 4 7% 6%	2536
	21st to end	Night	19% 62% 4 7% 7% 2	2130
March	1st to 10th	Night	49% 29% 3 7% 10% 2	4929
	11th to 20th	Night	42% 31% 12% 8% 6% 1	4980
	21st to end	Night	48% 29% 3 11% 8% 1	5466
April	1st to 10th	Night	23% 62% 3 6% 4 3	2026
	11th to 20th	Night	19% 66% 4 7% 3 1	1757
	21st to end	Night	22% 65% 2 6% 4 1	1710
May	1st to 10th	Night	34% 44% 12% 7% 2	2732
	11th to 20th	Night	24% 44% 14% 15% 3	2507
	21st to end	Night	32% 46% 13% 7% 3	2750
June	1st to 10th	Night	19% 66% 4 8% 3	1429
	11th to 20th	Night	17% 65% 5% 10% 2 1	1330
	21st to end	Night	21% 64% 5% 5% 5%	1330
July	1st to 10th	Night	33% 40% 8% 9% 8% 1	2175
	11th to 20th	Night	28% 40% 15% 12% 5%	2278
	21st to end	Night	24% 39% 11% 16% 9%	2776
August	1st to 10th	Night	37% 41% 9% 10% 3	2813
	11th to 20th	Night	25% 42% 10% 13% 10% 1	2809
	21st to end	Night	20% 39% 10% 18% 12% 1	3238
September	1st to 10th	Night	14% 61% 6% 12% 6% 1	1900
	11th to 20th	Night	18% 60% 6% 12% 4	2000
	21st to end	Night	15% 61% 6% 13% 5% 1	2130
October	1st to 10th	Night	34% 37% 7% 17% 5%	3800
	11th to 20th	Night	20% 37% 7% 22% 14%	3779
	21st to end	Night	26% 36% 10% 16% 12%	4147
November	1st to 10th	Night	25% 57% 7% 7% 4	2709
	11th to 20th	Night	26% 57% 5% 7% 4 1	2800
	21st to end	Night	26% 57% 4 7% 5%	2800
December	1st to 10th	Night	28% 37% 8% 21% 7%	4580
	11th to 20th	Night	35% 33% 6% 13% 11% 2	5233
	21st to end	Night	44% 27% 9% 13% 7% 1	7502

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	32% 24% 30% 15% 1	200
	11th to 20th	Day	31% 23% 29% 12% 5% 1	325
	21st to end	Day	18% 23% 39% 16% 4	440
February	1st to 10th	Day	23% 27% 31% 15% 4 1	400
	11th to 20th	Day	26% 28% 31% 11% 3 1	396
	21st to end	Day	22% 23% 35% 17% 3	337
March	1st to 10th	Day	26% 26% 36% 10% 2 1	500
	11th to 20th	Day	22% 26% 34% 15% 4 1	500
	21st to end	Day	30% 26% 30% 10% 4 1	550
April	1st to 10th	Day	34% 26% 27% 10% 2 1	500
	11th to 20th	Day	28% 27% 29% 13% 4	452
	21st to end	Day	28% 24% 29% 13% 6% 1	460
May	1st to 10th	Day	31% 23% 26% 16% 4 1	521
	11th to 20th	Day	26% 20% 27% 19% 7% 1	674
	21st to end	Day	24% 21% 33% 19% 3	735
June	1st to 10th	Day	30% 17% 31% 16% 5%	680
	11th to 20th	Day	23% 17% 33% 20% 6% 1	680
	21st to end	Day	25% 17% 27% 24% 6% 1	680
July	1st to 10th	Day	21% 14% 37% 20% 6% 1	670
	11th to 20th	Day	16% 9% 40% 25% 9% 1	668
	21st to end	Day	19% 10% 38% 25% 7%	665
August	1st to 10th	Day	16% 10% 37% 30% 6% 1	486
	11th to 20th	Day	18% 11% 34% 26% 9% 2	479
	21st to end	Day	15% 16% 33% 24% 9% 3	539
September	1st to 10th	Day	13% 15% 42% 21% 7% 1	490
	11th to 20th	Day	23% 13% 32% 21% 10% 2	490
	21st to end	Day	20% 17% 33% 21% 8% 2	467
October	1st to 10th	Day	23% 14% 30% 21% 11% 2	390
	11th to 20th	Day	23% 20% 29% 20% 7% 1	390
	21st to end	Day	27% 21% 32% 13% 6% 1	429
November	1st to 10th	Day	27% 23% 30% 12% 7% 1	395
	11th to 20th	Day	34% 21% 26% 13% 5% 1	400
	21st to end	Day	32% 23% 31% 10% 3	400
December	1st to 10th	Day	31% 22% 30% 14% 3	400
	11th to 20th	Day	31% 29% 27% 11% 1 1	385
	21st to end	Day	25% 26% 34% 11% 3	220
January	1st to 10th	Night	26% 23% 31% 17% 4	900
	11th to 20th	Night	27% 20% 30% 18% 5%	873
	21st to end	Night	19% 24% 34% 18% 4	880
February	1st to 10th	Night	27% 22% 31% 18% 3	800
	11th to 20th	Night	27% 23% 32% 15% 2 1	783
	21st to end	Night	22% 19% 35% 20% 3	660
March	1st to 10th	Night	25% 21% 34% 19% 2	800
	11th to 20th	Night	24% 18% 33% 19% 6%	800
	21st to end	Night	27% 17% 32% 19% 5%	880
April	1st to 10th	Night	31% 18% 32% 17% 3	626
	11th to 20th	Night	28% 16% 31% 20% 5%	567
	21st to end	Night	28% 17% 29% 19% 6% 1	570
May	1st to 10th	Night	28% 14% 30% 21% 6%	570
	11th to 20th	Night	27% 14% 28% 23% 7%	562
	21st to end	Night	20% 14% 42% 20% 4	616
June	1st to 10th	Night	29% 11% 31% 24% 5%	479
	11th to 20th	Night	21% 9% 34% 30% 5% 1	380
	21st to end	Night	24% 9% 28% 32% 6%	380
July	1st to 10th	Night	19% 8% 41% 23% 8%	370
	11th to 20th	Night	16% 10% 36% 31% 7% 1	426
	21st to end	Night	19% 7% 36% 32% 7%	623
August	1st to 10th	Night	15% 6% 36% 33% 10%	568
	11th to 20th	Night	17% 7% 31% 31% 13% 1	562
	21st to end	Night	14% 10% 30% 33% 12% 1	627
September	1st to 10th	Night	18% 10% 37% 28% 7%	570
	11th to 20th	Night	19% 10% 27% 32% 12% 1	670
	21st to end	Night	20% 13% 30% 27% 10%	760
October	1st to 10th	Night	22% 12% 28% 28% 10% 1	760
	11th to 20th	Night	23% 15% 32% 21% 8% 1	760
	21st to end	Night	31% 20% 28% 18% 3	836
November	1st to 10th	Night	27% 19% 29% 18% 6% 1	867
	11th to 20th	Night	27% 22% 28% 18% 5% 1	900
	21st to end	Night	29% 22% 29% 17% 3	900
December	1st to 10th	Night	29% 21% 30% 17% 3	900
	11th to 20th	Night	29% 25% 31% 13% 2	900
	21st to end	Night	30% 23% 25% 18% 3 1	990

Page generated at 2025-04-08 10:17:29. Version ac07

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